Well...
HIGH - you jump high
LOW - you jump low
DOLLY - suck your thumb while jumping
PEPPER - jump fast
SKIP - rope swayed from left to right, and you jump over it
HOP - hop instead of jump
JUMP - normal
CHOICE - you choose which you want
So, you do one of them, while people chant it on every jump, and the one you miss the jump on, the next person does, and it carrys on like that.