This is an easy way to get the Blue Shell achievement. I was able to get it on my first try.

• First go into the Career mode.
  
• Next, go into the SuperSport Championship.
  
• Then pick event #4 called The Mob.

This event has you play as a Hooper Vagrant while your 15 opponents are Bock Lithes. At the start of the race, just drive forward and to the right, against the wall.
Let everyone pass you and BOOM, easy achievement. :)

Please rate this guide up if you found it helpful. Also, if you want help with more achievements, check out my other guide: http://steamproxy.com/sharedfiles/filedetails/?id=534708108