if i find myself in a compromised starting position, like didn't change to a low enough gear at a sudden stop, i've taken to using the Flintstone Scoot n' Slide. No doubt others do this too: I sit on the seat back, about 2/3 of the way up towards the headrest, like you see Larry, Jason, Kevin, Joe, and others doing as a rest position while waiting for the race to start. Then do the Flintstone from that position....much more mechanical advantage than when sitting at the bottom of the seat....get up enough momentum, then just lean back and slide down, clip in, and off we go. ('we' being An Dubh [The Black] and myself of course)
Also use the one-legged pedaling, esp in a crowded start, sometimes Flintstoning along with the other foot for stability.