3 grand is usually where you start if you are really launching. Find a place where you can do a few. Then based on your wheel spin or lack there of, go higher or lower. Usually what I do (assuming no clutch stop) I will blip the throttle up to my desired launch rpm, blip it again a bit over and then start taking the clutch out as the rpms fall then right before/as (hard to explain) the clutch engages stomp the gas pedal. In the 318i that resulted in a perfect launch. In the M3 I do the same thing but do not push the pedal all the way down as quickly.