I'm playing on gaming laptop HP G62 with this configuration: VRAM 512 mb, RAM 4gb, Windows 7 x64.
I've optimized DayZ to almost 0 lags!
So here we go.

Step 0. First of all we have to enter the game with the default settings and then we have to exit immediately.

Step 1. Config settings:
Now go to "C:\User\Documents\DayZ\" and find the file "profilename.DayZProfile". You have to open this one with any word processor. Here you need to find these parameters:

• sceneComplexity=300000;
  
• shadowZDistance=100;
  
• viewDistance=1000;

Set the parameters as I did. Most online guides say to change tons of other parameters but I can assure you that the really useful parameters that have to be changed are those 3.

Step 2. Ingame settings
Now we go to "Configure" menu.
Here we can see "Field of view". Grab the point to 3/4 to the right side of column.


Enter the "Video" submenu.
"Overall Quality" parameter has to be "Custom" after we've changed config. If it's not, switch the parameter to "Custom"

Now we go to the "User Interface" submenu and set up "Resolution" to the "Windowed". I have to tell that this parameter doesn't decrease FPS and gives an opportunity to alt+tab the game without fear of game crush.

After we've configured "User Interface" we are returning to "Video" submenu and moving to "Quality".
I'd suggest to switch parameters to: "Objects" - Low, "Terrain" - Low, "Clouds" - Off, "Shadows" - Off.

Closing the "Quality" and moving to "Textures"
Here we have to switch "Video Memory" to Auto, "Texture Details" to Low and "Texture Filtering" to Disabled. This gives us the highest FPS over all other options.

Closing the "Textures" and finally go to "Rendering"

• "Antialiasing" - Disabled
  
• "Alpha to Coverage" - Disabled
  
• "Edge Smoothing" - Disabled
  
• "HDR Quality" - Very Low
  
• "Ambient Occlusion" - Disabled
  
• "Postprocess Quality" - Disabled
  
• Switch "Bloom" to 1/4 to the left of column.
  
• Switch "Rotation Blur" off.

After we've changed these parameters, we have to restart the game again.
Now we can finish the Ingame configuration.
Enter "Configure" -> "Video" and switch "VSync" to Disabled. Then the "Rendering Resolution" parameter as it's comfortable for you between 75% and 100%. You can try to switch the parameter to any option with the rule: Lower % higher FPS.
This is the difference:
100% (lagging a bit)
and 75% (zero lags)

Step 3. Launch options
After we've done with previous 2 steps we are going to Steam Client -> Library -> Right click on DayZ -> Properties -> Set Launch Optins and enter this parameters:
-nosplash - setting off the startup intro
-nopause - useful for ppl with 2 or more monitors attached
-winxp - use on your own risk, this may cause to unexcpectable game crush any time but increase perfomance up to 25-30%
How this has to be:

Step 4. Be safe and sound!
Play carefully! There are too much bandits these days! You are ready to challnge them :)
Thanks for reading. Hope this helped.