I'd start by completing your signature and let us know what platform and rig you play it on. Advice changes considerably based on those.
You might also take a read at the top of Asturbo's buglist thread at SMS's forum, so you don't get confused when a bug hits you and you think it's something you did wrong..!
A bit of info about what kind of racing or driving you prefer (road cars, race cars, historic, drifting, rallycross etc.) might help us help you, too.