NARC

* While coming out of any door, move the joystick Left. IMMEDIATELY after your character appears, move the joystick Up. If you do everything correctly, your cop will be 'stuck' to the wall, and will be able to walk on the wall to the next stage.

* Specific Advice For The Same Trick:
An easy way to get free lives is on the first level. Right after you leave the subway, keep your joystick pointed up. If you do this, you will 'stick' to the wall and nobody can touch you, though you can arrest tons of people (50 is the max). You can do this in other levels, though it does not seem to be as useful. One problem occurs right when you get out of the subway. There is a barrel which obstructs your path in/on the wall. You can just rocket it away if there are people behind the barrel (in respect to you). You can stay on the wall all the way to the passkey spot and into the door.

* To get ridiculous numbers of points and free men, you need to get to the end of the game, or at least where Mr. Big is. Once you've killed him (the little one *and* the big one), and you get to enter the treasure vault, just collect all the big gold blocks, and just wait. Don't do anything, just wait. After a while, the machine will send a pack of those annoying dogs after you. Let them kill you. You'll be sent back a stage in the game. And you have to fight your way back to the next 'bonus' exit door... once you do, mega-points and mega-men.

* Note the automatic teller machines present in a few places. March your character up to the machine and push into it; it should start spitting out money (evidence). Not HUGELY useful, but it's still kind of neat.