Powerful wind  [screen shot]
When you reach the first staircase In World 5-1, scroll forward until the wind starts to blow. Get on one of the steps (or ground), and face left. Release the B Button if you were holding it, and then rapidly tap Left on the Control Pad about five times. The wind should push you through the stairs! This will probably work in any level with wind...
-- [Found by Deezer]

Invisible platform  [screen shot]
Bring Luigi to World 1-3. When you reach the first "Scale Lift," stand on the left platform and let it go all the way down until it breaks off, then quickly jump to the small "mushroom platform" on your left. Now do a running jump (hold the B Button) to about where the right platform fell off, but a little lower. If you jumped at full speed, you'll touch an invisible platform for sure, but you're using Luigi, and the platform is no bigger than the one that used to be there, so it might take a few tries to land without sliding off.
-- [Sent in by avam@worldnet.att.net]