Umm... teach me! Seriously, tips?
One big thing that seems to set DC apart from other games, is that you are very severely punished for going off track and touching the barriers (although this does appear to have been toned down, there is at least one track where wall riding is a legitimate way of going faster), aim to stay away from the sides of the track at all times, even the dirt and gravel sucks a heck of a lot of speed away.
Many people try to brake far too late in an attempt to be fast, this is mostly a futile way to drive, most corners are better when you sacrifice entry speed for apex and exit speed, slow-in, fast-out, especially those with a bit of straight after it (ok, so the fastest was is fast-in fast-out, but lets keep it simple for now).
So, brake smoothly in a straight line, don't wrench the steering about, hit the apex and accelerate out carrying as much speed through the apex as possible, you DO NOT want to lift off the throttle once you have started accelerating out of a corner, if you do, then you either went in too fast, missed the apex, or started to accelerate too early.
Smoothness is key, keep cool, keep smooth.