If you are looking for the fastest way to level up your character in World of Warcraft, I would highly recommend you to take a look at Extreme Leveling Guides by Shawn Woods. It contains separate guides from 1 to 12, 13 to 70 and 71 to 80, and the entire presentation and graphics inside make the strategies very easy to understand and use. The auto-leveling mod has also helped my leveling efforts tremendously.
Once you learn all the strategies inside Extreme Leveling guides, you should have no more problems with your quests and you will find leveling very fun and fast. Compared to several other Wow leveling guides that I have experimented with, this one definitely has the best information, and it is definitely worth much more than what it costs.