"Load the game"
Just open the game and you'll get this.

"First Blood"
Kill your first enemy.


"Stronger than steel"
Pick up 35 shield buffs.


"Caterpillar"
Squash 200 enemies by running them over with your tank.


"Karma"
Die 100 times.



Best way to get this is in the 1st level. Pick up the shield in front of you and go left, running over the soldiers without shooting, then go up and pick up the second shield. You should die shortly afterwards. Repeat until you get them all.

Complete the levels 1, 2, 3 and 4 respectively.
The only tip I can give you here is to go slow and remember that your tank has more range that the enemies, hitting out of the screen. Once you know where the enemies are it should be pretty easy.