In any stages with either targets or enemies or anything else, if you kill or shoot every single one of them on that stage, you will get either 500, 500x???, 5000, or 5000x???. The ??? = anything. Remember, it will only happen if you kill or shoot EVERY SINGLE ONE OF THE ENEMIES!
While playing a "Target Shooting" level, keep on the lookout for scarecrows. Once one is found, shoot the torso of the scarecrow 8 times. The head will inflate, allowing you to shoot it for 1000 points. Do this with the two scarecrows in the level (the second one will only appear if the first has already been shot), and instead of taking you to the default third area, the game will bring you to an alternative area, with more gold targets.
When you shoot a scarecrows body 6 times and then its head you get 600 points!It's an awsome way to get points and you can shoot the body more times for more points!
On level 8, stage 3, when you're battling the Darknut, he will continuously shoot bats at you.
To easily kill lots (not all, of course) of the bats, simply hold down 'B' to load a bomb, and shoot!