High percentage moves are just moves that have a very high statistical chance of working (based on competitions). If you see one sweep/submission that is constantly being used successfully, it is probably worth studying.
One example would be the bow and arrow choke with the gi on. Most of the time when an elite black belt has back control, the bow and arrow choke is the first move that he goes for and usually finishes. It is just a matter of establishing back control.
Now a match from Davi Ramos, where he finishes his opponent with a nasty bow and arrow.