First, beat the world 5 boss as mini. Then you will unlock world 7. Beat the levels until you get to the three levels in a square. Go to the one with a patch of grass under it. Go through the level until you see a bunch of Bullet Bill cannons. On the left side there should be three, and on the right side 2. Go back and jump on the red koopa troopa. DON'T double jump. Pick up the shell and hold it. Get on top of the Left Cannons and throw the shell. then get on the bricks and wait and you will get infinite 1-ups!