Questing is generally slow until about level 20, this is because many of the quests are collections and have level requirements that are intended to be reached by solo play. There are also a great deal of collection quests early on and your somewhat constrained to your starting zone of choice. After 20 you get more choices, for example you can finish all dual-boxing friendly quests in Ashenvale, Hillsbrad, Ghostlands and stonetaleon if needed.

I'm sure you'll find a lot more info in other similar threads.