Rotate the analog stick and jump.
Simple huh? Yeah. But its very useful.
Now, Super Mario Sunshine may seem like an easy game, but for those people that want to get 100%, or just get stuck on some levels, heres a great tactic.

Normal: Lets see.... The spin jump... High? Check. Long? Check. Cool? Check. It can get you where you need to go. Use it, the wall jump, and you got even higher.

Spray Nozzle: If you use your standard spray nozzle while doing this, you will find it very useful. It covers a very large area while keeping you squeaky clean. Its great on time clean up levels, or any level like the one with the good preading, multipling manta rays.

Hover Nozzle: Anywhere you need to go, this will get you there. Just spin jump and hover at the peak. Or spin to wall jump, then hover. You can get anywhere.

Rocket Nozzle: Charge it at the right time so you blast off at the peak of the spin jump. Reach for the sky, Mario!

Speed Nozzle: From what i know, it does nothing... But it looks pretty damn cool!