I like that you assume that anyone here has ascended from noobhood.
But in seriousness, I learned to stop being a noob by making a whole lot of really noobish mistakes and learning from them. Do you have any previous MMO experience? Having played a few others in addition to WoW, I can say that there are a number of lessons that will carry over. But the most important thing you need to not be a noob in any MMO is patience, especially for the real human beings at the other end of the characters you group up with. That and an ability to notice when you're standing in fire.