some check your ip, some have a cd at the VG vote page. some have both, some just one of those 2, dependant on what works where. Haha!
Best thing you can do is look at the watch when you vote and wait 12h on your own. That way you dont waste anything. And you will surely not get banned when voting on only 1 account, no matter how often you try it on that one account, as there are those instruments in place that keep you away from abusing automatically.
One of the voting sites never usually registers so people voting usually get 2 vote points instead of 3, anyway to fix that?