How do I know what moves have more priority than others?
It usually tells you that the move will go before others.
Additionally, there are two abilities that give priority to certain moves. Prankster gives priority to all status moves, while Gale Wings gives priority to all flying type moves.
Heres a list of all moves with priority: http://www.serebii.net/games/speedpriority.shtml
Here are some examples:
The words in bold are words related to fast.
Hope I helped!