This is difficult, but you know what they say - practice makes perfect! I obtained this achievement by splitting the game into sections and then concentrating on perfecting the technique that worked best for me on each part. The sections are as follows:
Zombies of the Grassy Meadow - Simple section. Just keep moving in a circular pattern and spraying. When the music jumps in tempo, expect a surge of zombies!
Zombies at the Diner - The checkered background reminds me of an old-skool diner. This section is also relatively simple. The snakes are the most threatening enemy so try to keep some distance.
Poison Green Gas Clouds from Space - Easy...if you don't shoot the clouds. Just avoid, take it easy, and relax.
Ska Studio Zombies - Here is where the game starts to get intense. You really put your zombie shooting skills to the test here. It is critical to have a power-up at all times! My favorites: shield, triple-green thingy shooter, and the flame thrower. In a pinch, I grab the triple ping-pong ball shooter.
Geometry Wars with Zombies - Aarrrrgh!!! I hate, hate, hate the neon diamond shapes of death. My instinct was to play this section Geometry Wars-style - circle the level and shoot ahead. Didn't work. Solution - stay in the same relative location and use subtle movements to dodge incoming diamonds. I relocated whenever green blobs or snakes started to become a bother.
Death Metal Angry Faces - I think this part is easy. Those angry faces are mean, but they don't move too much. Watch out for the snakes though! They are sneaky.
Epic Finale on the Grassy Meadow - If you've made it this far without dying, you ain't need no stinking advice. You just got to seal the deal. So grab your favorite power-up and earn that 10G. You can breath again once the achievement pops!