hey, welcome to the site.
Some general SA2B tips to get you started, despite the fact that I'm lamer at it than other people:
-Spindash abuse will get you better times. If you go down a hill, quickly charge a spindash and release so you can move down the hill ASAP.
-Spindash-jump to reach far away places without much effort. Just charge a spindash, release, and immediately jump.
-Search for alternate ways to get to the next area in the stage rather than following the main path. Often, the main path isn't the fastest one, so experiment with everything.
-When you score attack, bear in mind that each second costs you 20 points (iirc). If you go after lots of rings, be sure that you're getting them as fast as possible, because although "the faster, the better" is true, remember that rings are worth 10 points each, too. Focus on more "direct" score (rings, enemies) than time, but don't completely ignore time altogether.
-Watch some videos of enemies/competitors/dark sides/friends with good skills. Familiarization with almost any game is spread by those who indirectly spread their stage knowledge and tricks through videos.
-Like Mike said, if you ever want some tips on a game, just contact the champions or main competitors of the game. Just check out the rankings to know who they are.
As they say in Starcraft, gl hf ka dd ds!