Chapter 2 - Test Chamber 06; «Final Transmission» - Find the hidden signal in one of the Rat Man's dens

Difficulty - Medium; When at the switch near the exit of Test Chamber 6, hit the switch and wait for all the trash to fall. Retrieve the radio from wherever it landed and go back to the switch. On the left wall at the opposite end of the chamber, there will be a portal-able surface; remember where this is. Portal back to the start of the chamber with the radio. Place a portal on the portalable-surface mentioned earlier and the other portal on the portalable surface the Aerial Faith Plates will throw you into, jump on the Aerial Faith Plates, and you will fly into one of Rattman's Dens—taking the radio in here will get you this achievement.
http://www.youtube.com/watch?v=-rtosjNiaNs

*Chapter 2 - Test Chamber 06*; «Drop Box» - Place a cube on a button without touching the cube

Difficulty - Easy; In Test Chamber 06 of Chapter 2, stand at the switch and place one portal on the right-hand sloped surface. Place the other portal on the panel above the button and press the switch twice. Alternatively, press the switch in Wheatley's very first test chamber.
http://www.youtube.com/watch?v=FiXvbjr6EN0

Chapter 2 - Test Chamber 07; «Preservation of Mass» - Break the rules in Test Chamber 07

Difficulty - Easy; To obtain this achievement you will need to bring the Companion Cube with you through Test Chamber 7's exit door. To do this you must solve the chamber as you normally would, but as you reach the exit you will need to place a portal on the other side of the door and place another Portal on any other accessible ground. Pick up your cube from the Super Button and use your accessible Portal to reach the other side of the door. This will grant you the achievement.
http://www.youtube.com/watch?v=rfGU7NA2_4A

Chapter 3 - Test Chamber 10; «Overclocker» - Complete Test Chamber 10 in 70 seconds

Difficulty - Medium; Self-explanatory.

http://www.youtube.com/watch?v=ahA2wc5GGGg

*Chapter 3 - Test Chamber 15*; «Pturretdactyl» - Use an Aerial Faith Plate to launch a turret

Difficulty - Easy; In Chapter 3, Test Chamber 15, place a turret on an Aerial Faith Plate. This may also be done in Chapter 2, Test Chamber 06 where a turret is sent out as garbage.
http://www.youtube.com/watch?v=Yvq9rvHK-ro

Chapter 4 - Test Chamber 21; «Good Listener» - Take GLaDOS' escape advice

Difficulty - Easy; As you escape, GLaDOS invites you to enter the final test chamber. She's even solved it for you. Do it.
http://www.youtube.com/watch?v=KbTXHuytW6g

Chapter 5 - Turret Control Center; «No Hard Feelings» - Save a turret from redemption

Difficulty - Easy; During your escape, walk along two Turret Redemption Lines. On the second one is a mostly-intact turret, signposted by its laser. Pick it up.
http://www.youtube.com/watch?v=LtSBpbmN820

Chapter 5 - Turret Control Center; «Scanned Alone» - Stand in a defective turret detector

Difficulty - Easy; In Chapter 5, remove the master turret from the template scanner in the turret factory control room, and then step into the scanner.
http://www.youtube.com/watch?v=D55ExYZ_06w

Chapter 6 - Beyond the Seal + Reconciliation; «Door Prize» - Examine all the vitrified test chamber doors

Difficulty - Medium; There are two sets of three vitrified doors in Chapter 6. The first set is on the upper catwalk in the lake area, immediately after the hatch. The second set is on a catwalk opposite the entrance to Pump Station Alpha; exit the lift and turn to the seven-o'-clock position. The third set is in the room above the control room where you find potato GLaDOS. Walk into the room from the top catwalk. Jump on the furniture in the back-left corner and go through the doors.
http://www.youtube.com/watch?v=sYbO61tq0bk

*Chapter 6 - Enrichment Sphere #3*; «Schrodinger's Catch» - Catch a blue-painted box before it touches the ground

Difficulty - Medium; On Chapter 6, Enrichment Sphere 3 save the game before dropping Repulsion Gel on the cube. Release the gel and try and catch the cube; if it hits the ground, load the earlier save. An alternate method of obtaining this achievement is to drop a little bit of Repulsion Gel on the cube, and then before it breaks out of the glass, drop water on it to stop the bouncing. Simply walk up to the cube and pick it up without touching the ground to get the achievement.
http://www.youtube.com/watch?v=LxOGKVbdBgk

Chapter 6 - Reconciliation; «Ship Overboard» - Discover the missing experiment

Difficulty - Easy; At the start of 1970s Aperture, go to the top catwalk. Follow it to the room, and jump on the furniture in the corner to get to the doors. Step outside to receive the achievement.
http://www.youtube.com/watch?v=nyHX95h3x_0

Chapter 7 - Enrichment Sphere #4; «Portrait of a Lady» - Find a hidden portrait

Difficulty - Easy; Immediately after Enrichment Sphere 4 in Chapter 7 is a closed gate, a portalable panel, and an Emancipation Grill that leads directly into Enrichment Sphere 5. Portal over to a second portalable panel beyond the gate, and enter the office to find the portrait.
http://www.youtube.com/watch?v=92UJoHbwDMU

Chapter 8 - all chambers; «Smash TV» - Break 11 test chamber monitors

Difficulty - Hard; In these test chambers, Wheatley's TV monitors are able to be smashed in the following ways: (this must be done in one run.)

• Test Chamber 1:Lift up a box using the funnel (make sure you are on the lower section) and, using its now gained height, fling it at Wheatley.
  
• Test Chamber 2:Do basically the same thing from Test Chamber 1.
  
• Test Chamber 3:The same as Test Chambers 1 and 2, but make sure you are in the first section of the chamber.
  
• Test Chamber 4:Pick up the turret behind the button and aim it at Wheatley. It will not shoot until you let go, setting it upright.
  
• Test Chamber 5:There are two monitors in this chamber. They both are smashed by lifting a box in a funnel and flinging it, but the exit portals are in two different locations. The first is on the wall in which the funnel is being projected on, around the center (This will take experimentation.) The second is on the very right of the angled surface that you go through on your way to the exit.
  
• Test Chamber 6:Launch yourself on the Aerial Faith Plate.
  
• Test Chamber 11:Burn him with the Discouragement beam and the Redirection cube. you will need to use the box to get the beam on a portal conductive surface, then use portals to get the beam to hit Wheatley.
  
• Test Chamber 12:When you are in the place where you would normally use the cube to open the door, burn the monitor.
  
• Test Chamber 15:Do the same thing as Test Chambers 1, 2, and 3.
  
• Test Chamber 16:(Tip: this is extremely hard to get in one try. Save at every point noted.) Do the test normally, however at the part where you coat turrets in Repulsion Gel (save before this) You must only coat two of the turrets, leaving one alive. (save now as well) Then, using one of the portal surfaces on each side of the turret platform, jump on the platform while pressing the crouch button to avoid bouncing on gel. Grab the one remaining turret, and use it to shoot Wheatley and earn the achievement.
  
  An easier way to do the "Hard" last one is. Go behind the black strip of wall infront of the turret (After you bounce the other too) And then you wait for him to start shutting down and run out and grap im. That way you can get him during the time it takes him to close himself and re open.

http://www.youtube.com/watch?v=xBnBboJErHk

Chapter 8 - Frankenturrets; «You Made Your Point» - Refuse to solve the first test in Chapter 8

Difficulty - Easy; Enter Wheatley's very first test chamber (with the "moat area"), but don't press the switch and don't step on the button.
http://www.youtube.com/watch?v=OJrfz5BRWKo

Chapter 9 - Mash-up; «Pit Boss» - Show that pit who's boss

Difficulty - Easy; At the start of Chapter 9, when Wheatley asks you to come back, go back. Then do as he says.
http://www.youtube.com/watch?v=JxLZvSBNGUg

Chapter 1 - Introduction; «Wake Up Call» - Survive the manual override

To achieve this achievement you simply need to enter the old testing track after waiting for Wheatley to crash through the Docking Station wall. You should then be able to receive the Achievement automatically.

Chapter 1 - Her Chamber; «You Monster» - Reunite with GLaDOS

This achievement will be obtained as soon as you wake up GLaDOS during the first chapter of the game.

Chapter 2 - Test Chamber 01; «Undiscouraged» - Complete the first Thermal Discouragement Beam test

As your first test of the second chapter, you will be treated to a simple puzzle involving Thermal Discouragement Beams. Complete this test and you'll be awarded with the achievement.

Chapter 3 - Test Chamber 11; «Bridge Over Troubling Water» - Complete the first Hard Light Bridge test

During the third chapter, Test Chamber 12 will introduce the new Hard Light Bridge. Similar to the Undiscouraged achievement, you will need to complete this introductory chamber to obtain the achievement.

Chapter 4 - Test Chamber 21; «SaBOTour» - Make a break for it

Half way throughout Test Chamber 21 you will be interrupted by Wheatley, who will offer you an escape route. The achievement will be obtained as soon as you begin your escape.

Chapter 5 - GLaDOS' Lair; «Stalemate Associate» - Press the button!

Upon facing GLaDOS for the second time, you will be asked to place Wheatley in an Aperture Science Core Transfer Receptacle. After a disagreement between Wheatley and GLaDOS on whether the process should go ahead, you will be asked as a Stalemate Associate to press the Stalemate Associate Button. Doing so will reward you the achievement.

Chapter 6 - Enrichment Sphere #2; «Vertically Unchallenged» - Master the Repulsion Gel

This achievement will be awarded after a series of Repulsion Gel based tests during Chapter 6.

Chapter 6 - Reconciliation; «Tater Tote» - Carry science forward

Near the end of Chapter 6 you will reunite with GLaDOS in her potato form. Simply pick her up to receive the achievement.

Chapter 7 - Enrichment Sphere #5; «Stranger Than Friction» - Master the Propulsion Gel

Identical to how Vertically Unchallenged worked, you will need to complete a series of Propulsion Gel based tests during Chapter 7.

Chapter 7 - Enrichment Sphere #6; «White Out» - Complete the first Conversion Gel test

Complete the first Conversion Gel test.

Chapter 8 - Frankenturrets; «Dual Pit Experiment» - Do the same test twice

Complete Wheatley's very first test chamber twice.

Chapter 8 - Test Chamber 15; «Tunnel of Funnel» - Master the Excursion Funnel

Complete Chapter 8 Test Chamber 15.

Chapter 9 - Mash-up; «The Part Where He Kills You» - This is that part

Given at the start of Chapter 9.

Chapter 9 - Finale; «Lunacy» - That just happened

Complete the Single-player campaign.

All cooperative chambers; «Asking for Trouble» - Taunt GLaDOS in front of a camera in each of the five co-op courses

Difficulty - Easy; In each of the co-op courses, find a room with a camera and perform a gesture toward it. This does not need to be completed in one session.

Course 2 - any 3 chambers; «Triple Crown» - Solve 3 co-op chambers in the Mass and Velocity course in under 60 seconds each

Difficulty - Medium; For this achievement you need to complete 3 of the 8 stages of the Course 2 in under 60 seconds. You do not need to do them in a row or in any specific order. Stages 1, 2 and 4 are very easy to complete within that time. Make a plan with your partner on who does what on the stages and practice the stages you and your partner find easy. Then make your attempt on the achievement
http://www.youtube.com/watch?v=2WcfOgXUsJ8

Course 2 - Chamber 6; «Iron Grip» - Never lose a cube in Chamber 6 of the Mass and Velocity co-op course

Difficulty - Medium; In the area within this test that gives this achievement its difficulty, timing is everything. Make sure you and your partner know what you're doing before attempting this. If you lose one box, go back to the hub and try again.
http://www.youtube.com/watch?v=UG6o3CR3caU

*Course 3 - Chamber 1*; «Empty Gesture» - Drop your co-op partner in goo while they are gesturing by removing the bridge under them

Difficulty - Easy; Self-explanatory. Do this in a level with Hard Light Bridges. Usage of the timer is recommended.

Course 3 - Chamber 3; «Portal Conservation Society» - Complete Chamber 3 in the Hard-Light Surfaces co-op course using only 5 total portal placements

Difficulty - Hard; This achievement is possible to obtain with only one set of portals. Place one portal at the receiving end of the Hard Light Bridge, then place the other portal on a nearby wall. Enter the portal on the wall and walk over to the bridge emitter. Move on the emitter so that you can see the white surface of the overhead panels, then fire a portal so that the Hard Light Bridge runs under the Vital Apparatus Vent. Press the button in the center of the wall by the Light Bridge and have your partner catch the ball that drops out of the vent. Place the ball on the receptacle and proceed into the next part of the chamber. Fire a portal at the receiving end of the Hard Light Bridge, then line up the second portal on the ceiling so that using the Aerial Faith Plate bounces you off the vertical light bridge and into the exit area.
http://www.youtube.com/watch?v=6V2-7DwHgsM

*Course 3 - Chamber 6*; «Can't Touch This» - Dance in front of a turret blocked by a hard light bridge in co-op

Difficulty - Easy; Course 3, floor 6 of co-op is one place to get this achievement. Use the dance gesture while being protected from turrets by a hard light bridge.
http://www.youtube.com/watch?v=A-mOIINmA_k

Course 4 - Chamber 9; «Party of Three» - Find the hidden companion cube in co-op test chamber

Difficulty - Easy; In the final area of the excursion funnel section of co-op mode, you will be outside the official testing track. In one of the many times you and your partner are floating through a funnel, if you look straight to your left, (on the same wall where your partner shoots Hard Light Bridges) you will see a portal conductive surface that you would not normally pay attention to. Shoot a portal there so that the funnel is coming out of it and you float through the funnel. If you look to your left you will see a companion cube behind doors that will open. You will then hit a spike wall and die, so don't try this while attempting Still Alive.
http://www.youtube.com/watch?v=Yz8Z0PWxSUQ

Course 4 - all chambers; «Still Alive» - Complete Course 4 with neither you nor your co-op partner dying

Difficulty - Very Hard; Get through the excursion funnels course in one run... with no deaths. Watch out for test chambers:

• 3 - Voice chat, the timer, and a clear understanding of the course/practice are highly recommended.
  
• 6 - Make sure you do not make a very common mistake. Do not go into the spikes at the end of the excursion funnel/practice.
  
• 8 - This is a trust test so do not fool around. It's easy if you try/practice.
  
• 9 - Do not shoot the wrong portal whether you are doing the Hard Light shields or the funnels... practice. Also, don't try to get Party of Three (see above).

Practice on all of these stages! That cannot be stressed enough!
http://www.youtube.com/watch?v=YK5YMgG6arM[/td][/tr][/table]

Course 5 - Chamber 6; «Talent Show» - Never lose a cube in Chamber 6 of the Mobility Gels co-op course

Difficulty - Medium; Self-explanatory, but make sure you and your partner know what you're doing.
http://www.youtube.com/watch?v=rXYTgfRpk5o

Calibration Course; «Professor Portal» - After completing co-op, complete Calibration Course online with a friend who hasn’t played before

Difficulty - Hard; Find random partners online, and immediately leave the game if you do not see the opening film. when you find a beginner, exit the game, friend them, and invite them. This will take a long time depending on how lucky you are.

«Gesticul-8» - Perform all 8 gestures of your own volition in co-op

Difficulty - Easy; Once you get all the gestures, simply perform them.

«Rock Portal Scissors» - Win 3 co-op games of rock-paper-scissors in a row

Difficulty - Easy; After unlocking the Rock Paper Scissors Gesture, just keep on using the gesture with your partner over and over again until you get the achievement.

«Air Show» - Perform 2 aerial gestures before touching the ground in co-op

Difficulty - Easy; During a long jump, gesture twice before you hit the ground. Alternatively, create an infinite fall by placing a portal on the ceiling and one on the ground beneath it or do the gestures in an Excursion Funnel.
http://www.youtube.com/watch?v=qKpJyCRqinc

«Friends List With Benefits» - While playing co-op, hug 3 different people on your friends list

Difficulty - Easy; Self-explanatory.

«Narbacular Drop» - Place a portal under your co-op partner while they are gesturing

Difficulty - Easy; Self-explanatory.

http://www.youtube.com/watch?v=VH9jtfL2GKU

«Four Ring Circus» - Enter 4 different portals without touching the ground in co-op

Difficulty - Easy; Course 1, your friend needs to place portals next to eachother on the floor, which is under a ceiling where you can place your portal. Shoot a portal next to your friends portals and the other one on the ceiling facing one of your friends portals. Fall through your portal and when you go through one of your friends portals, you'll be facing the ceiling again. Then you must shoot the portal on the ceiling to the place where you are about to go. Then wait for a while as you are falling through the portals and the achievement will appear.
http://www.youtube.com/watch?v=Ovc6Cl0Lwok
http://www.youtube.com/watch?v=JKqUxfpkRIU

Calibration Course; «High Five» - Celebrate your cooperative calibration success

Just complete the calibration course in co-op to get this achievement.

Course 1 - Chamber 6; «Team Building» - Complete all test chambers in the Team Building co-op course

Finish all 6 stages in course 1 of co-op mode.

Course 2 - Chamber 8; «Confidence Building» - Complete all test chambers in the Mass and Velocity co-op course

Finish all 8 stages in course 2 of co-op mode.

Course 3 - Chamber 8; «Bridge Building» - Complete all test chambers in the Hard-Light Surfaces co-op course

Finish all 8 stages in course 3 of co-op mode.

Course 4 - Chamber 9; «Obstacle Building» - Complete all test chambers in the Excursion Funnels co-op course

Finish all 9 stages in course 4 of co-op mode.

Course 5 - Chamber 8; «You Saved Science» - Complete all test chambers in all courses of co-op

Complete the Co-op campaign.