I DO NOT TAKE ANY CREDIT FOR THESE GUIDES.
12-20 http://www.wow-pro.com/node/660
21-31 http://www.wow-pro.com/node/739
31-40 http://www.wow-pro.com/node/755
40-51 http://www.wow-pro.com/node/880
51-60 http://www.wow-pro.com/node/908
They all run off one another, and you can pick up in the middle. Just go to your level range, then find your level.
Great guide, leveld my guy to 41 in four days
As I said at the top, I did not make these, I'm just giving you guys the links so you can use them. I take no credit for them. Enjoy