Post by Sagerauru
First of all, it is hard to direct you to a proper area to train in if we have no knowledge of which faction you are playing on, and sometimes, which race you play. I'd have to assume from you saying that you quest in the Ghostlands and Barrens, you are playing on the Horde side. If that is the case, I am thinking that the Ghostlands might be a bit low for you, and that would be why you aren't getting very much experience out of it.
Also, you mention of having friends who are level 10 and others who are level 40. You have to realize that everyone quests at their own pace, and not everyone is going to be level 80 overnight. Also, they may have been a higher level when you met them, so you really couldn't make a fair judgment there.
Some people write "leveling guides", which supposedly help people to level faster. I've tried one for an Undead Mage I had, but I didn't really think it made that big of a difference when I was using it compared to when I wasn't. However, one free guide I hear a lot of people talk about is Jame's, which can be located
here.
Since I haven't really leveled a Horde character, it is hard for me to direct you to the correct place, but I hope that the link to the guide above will help you. Good luck questing!