Rango

This achievement is fairly simple. I achieved this while playing on my first play through on hard. I unlocked this my first time trying. Now that you know about how easy it is, lets explain what to do.

Mission: Zombie Invasion

Okay so this part is right after you defeat the enemies in the graveyard with the exploding red golf balls. You will have to hop on a bat ( CUT SCENE PART SO DON'T WORRY ABOUT LOOKING FOR IT) What I did was don't shoot as much and focus on dodging everything. This achievement is really easy just don't crash into anything. Look out for things that fall down near you. Say it starts falling from the left go all the way to the right. Look out for things that shoot out from underneath as well. The enemies don't seem to bother you. They just seem to give you stars, but don't risk your life on them seeing it would suck because you are about half way into the level.

What Pickle Squid said is spot on. I just wanted to add that if you do accidentally get killed like i did, all you have to do is hit the guide button and go to the dashboard. Then just reload your game and continue. I did this and still got the achievement with no problem. This would also probably work for the roadrunner achievement if that one is giving you a tough time.