Read the Manual
This may seem like an obvious tip, but when you buy World of Warcraft from the store, it includes a manual. It's not just there to fill the box. If you bought the game online and didn't get the manual, Blizzard's website has everything you'd need anyway (no excuse for those who don't like books). People in the game are normally happy to help beginners, but if you're constantly asking questions that are easily answered in the manual, people will get annoyed and think rather unkind things about you. Of course the sort of people who absolutely refuse to follow instructions probably wouldn't have read this far so we're probably telling you what you already know but, hey. Be aware that some people who play the game are genuinely clueless and quite happy to stay that way. Try to stay calm when you meet them.