1. Use the Feisar or AG systems to unlock the whole game (win championship race on Venom to unlock Rapier, win champ. race on Rapier to unlock Firestar).
2. Focus on one track at a time and race it until you know where all speed pads and weapon pads are, and what the best race line is on each class. THEN, to lower your times, NEVER race unless you get the turbo start, whether you are on single race or time trial. Find out which ships are particularly suited to a track if you have the time/patience to handle the Qirex/Auricom.
3. Watch as you race to see at what points in the track your speed drops below max. These are the places where you should be employing your turbos. Link up all of the speed pads on the track that you can, the only time you can usually afford to miss them is when you are on a turbo (or racing Silverstream). Never use a turbo if you are going to end up bouncing a lot (unless you are on single race and going for record race time...you may get more turbos that race).
4. Finishing a race with a turbo may seem like a great finish but you are wasting the tail end of your turbo, try to use it elsewhere on the track where you get its full impact.
5. DON'T BOUNCE!!! Once your ship bounces more than once you've wasted a LOT of time. Learn to control the bouncing by race line or nose up/down.

That's all my tips for now.