jeeez... i spend all day fixing cars for a living, then come home to this!
ok, first of all, check your interior light is working. the older beetle fuseboxes were pretty wierd, and alot of things earth out through that light.
next check your feeds at the starter motor. there should be 1 really thick wire, thats your perminant live feed straight from the battery so you should have battery voltage on that.
the other wire on the starter is your feed from the ignition switch. get someone to turn the key while you probe that wire. when the key is turned you should have battery voltage. if you have power there when the key is turned, but the starter doesnt turn, then the system is ok, but there is a fault with the starter. try removing it and cleaning up where it bolts on (it earths itself through the bolts)
if you got no power there, then its a case of fault tracing the rest of the system, which i can talk you through after you checked them first bits.