"Best way" and "Safest way" are polar opposites. Basically, your main concern is that you don't launch hard frequently. But the occassional odd stoplight launch should be no problem for your Porsche. DON'T SLIP THE CLUTCH. Just drop her, and get it engaged so it doesn't go up in a cloud of smoke. I recommend, for a street launch, a 3,000 rpm quick drop. The magazines have been doing 4,000 grand launches, but I worry about the clutch at those revs. Fine for a magazine, they're driving a rental, what do they care? But for your own car, 3,000 should be tops.