Despite popular belief, this does not have anything to do with violent acts with both feet upon one's head, and is wrongly thought to become associative with the extreme neo-fascist ideas of cult film "American History X"
Despite unpopular belief, the term or idea wasn't made famous on Rancid's "Roots Radicals" song on the "Out Come The Wolves" album, neither.
It is also referred to as "skanking", which has it's origins in Jamaica, also. This is a perfectly respectable name.
To moonstomp conventionally, it is suggested that you raise your left leg along with your left arm and produce a low kicking movement towards the ground in front while making a slow and gentle "punching the air" movement with your fist, sweeping it behind your right leg and doing the same movement symmetrically with your right leg and right arm and thus repeating, to the rhythm and tempo of the ska or dub song, until the end of the song.