Seeing Stars
You can make it through World 7-3 much easier if you are able to maintain invincibility. You achieve invincibility by getting a star out of a question block or by using a star from Mario's item collection before you begin the level. After you get your first star, run to the right as quickly as possible, hitting the question mark blocks as you go to get more stars. If you do this quickly enough, you will make it to the end without taking any damage. The same trick is useful for World 7-7.
Two Extra Lives
Before beginning World 7-4 use an item from your collection to become a raccoon (the leaf) or Tanooki Mario (the raccoon-like suit). Build up speed by running to the right, and fly over the wall above the pipe. Over this wall, you will find two hidden 1-Up green mushrooms to add to your stash of extra lives.
Banish Boom-Boom
Your frequent nemesis Boom-Boom is back in the second fortress level of World 7. Use the ledges above the floor to get the height advantage on this adversary. Try to jump on him quickly three consecutive times, allowing a slight pause between blows due to the protective spikes that cover him after each hit he takes.
Airship Battle
You will battle Ludwig Von Koopa as you are making your way through the airship. Each time Ludwig jumps and hits the ground, the earth will tremble, temporarily paralyzing you. Jump into the air before he lands to prevent this. Ludwig attacks with smoke rings shot from his wand. Dodge these attacks and jump on his head. Three hits will take him out and send you to the final World 8.