Secret Third Areas
While playing a "Target Shooting" level, keep on the lookout for scarecrows. Once you see one, 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 and instead of taking you to the default third area, the game will bring you to a secret area.
On the level with the birds carrying targets you are told not to shoot the birds. If you do shoot them, they drop the target. If you can shoot the target while it falls you will get more points than if you had just shot the target while the bird had it.