When launching off the line with a limited-slip differential (lsd) or locking differential the preparation begins on the warm up lap. As you leave the dummy grid do your best to lay a couple of big black lines. Spin the wheels vigorously to lay down the rubber.
On the remainder of the warm up lap keep working to heat up the tyres, especially on the driven axle. When you return to the grid park in exactly the same place, making sure your driven wheels are on-top of the black lines of rubber you previously left.
At the ‘5 second’ board bring the revs up to approximately 3/4 maximum and select 1st gear with the clutch down. The moment the red lights go out sidestep the clutch to re-engage it with a ‘snap’ and give the gas a quick stab. The tyres will get better grip on the rubber you previously left on the track but you want the wheels spinning. Its easier to hold the tyres just over the limit of grip by judging throttle opening than it is to balance throttle AND clutch slip.
As the tyres start to grip up feed into full throttle and only shift up when you reach peak revs AFTER your tyres have gained full traction, not when they are still spinning.