I find feathering the throttle (e.g. laying off the acceleration, then back on, then off, on etc) is often times more rewarding in correcting trajectory or getting the right angle mid turn, than actual braking, the latter dropping speed too much. The other thing is the basic fundamental of racing which is slow in, fast out on harder corners. You want the best maximum exit speed, so try and set up those harder corners so that you're only needing to brake at the start, and can accelerate out with full throttle on the exit, building up maximum momentum and speed for the oncoming straight. If you overcook the corner and start going too wide, feathering the throttle or just laying off the gas with some sharper steer till you're back on the right line.
The other thing is, try not to be shy about mildly cutting corner apexes, even if it means one side of your car cuts some dirt or rumble strip. Often in doing this you can shave off some added time as your cornering distance will be reduced, as will the amount you need to slow down for the turn. However, be careful not to do this with certain vehicles or on certain angles, especially longer turns, as you will glue to strip or dirt and get drawn in or lose traction.
The only other thing I can thing off as a basic, is that with some of the faster and more crazy hyper cars (Venom, One:1 etc) sometimes gradually applying acceleration will prevent you from swerving about and losing traction. Otherwise you only really want to hammer it down when your wheels are completely straight, or there isn't too much of a camber or angle to the road.