At the title screen, press the directions given with Controller 2 and Start with Controller 1.
Go to the first green soldier and place yourself in a position so that a massive number of troops come onscreen. Now hold the fire button and get slaying. You will receive an extra life - up to a max of 13 - for 100 men.
Plug in a NES advantage.
Start the game at the first level and find the first enemy. When you do, if you stand in the right spot, he will keep appearing no matter how many times you kill him.
(notice when you kill an enemy, go backwards, then change directions again, they appear in the same spot again. try that with the first one)
When you do find the right spot,making sure that the shots shoot rapid-fire with the B button held down with turbo ON, tuck the button into the corner so it is held there. You can then leave the game while it blasts enemies up. You can get 22 lives with 10,000 points