Do quests. Try to enjoy the lore and story because there is a LOT there. Most people are just too busy hacking and slashing to read it all, though.
For a priest, figure out what play style you are focusing on: healer? damage? jack-of-all? Solo or group? This is where the builds and talent points come in.
The WoW forums are horrid. Try many of the other fan sites as they tend to be more informative in general. There's a lot of (way too much) complaining on the official forums.
"If the people we love are stolen from us, the way to have them live on is to never stop loving them. Buildings burn, people die, but real love is forever."