Staying alive:
Never stay still, even if you are trying to shoot someone or something.
If you move around, it will be harder for the Tan army to hit you; same
with the Bosses. If you miss an enemy, turn around and come back for
another pass, but do not stay still. For heavy populated areas, go
forward but weave left and right as you do so. This will help keep you
alive until the next health bag.
Weapons:
Try to get the Bazooka and the Flamethrower's power to maximum. Use the
Bazooka as your main weapon. It can blow up obstacles as well as cause
heavy damage. If you find yourself unable to kill an enemy near you, you
can quickly change to the Flamethrower and melt them, then change back
to the Bazooka.
Sink the Shark Submarine:
You must sink the Shark Submarine at the end of level 2. First, kill all
the tan soldiers that appear. Hold L1 and press the Right Analog-stick
to aim for the gun turrets on top of the submarine. Destroy the turrets
to sink it.