I try to keep my revs right before redline and I feel I get good starts. The trick is not redlining 1st-2nd, 2nd-3rd. That can be tricky, for me atleast.
I see a lot of people throw the hammer down on the line waiting for the lights to go off. If you pay attention to the car temps this will overheat the engine before the race even starts (which one would think would kill power). Try to work the throttle so you can hold revs without hitting the limiter and once you start rolling you can go into more/full power. usually gets me off the line fairly well