Horde Questing by Level
Making a run to level 80? If you are having trouble getting through a particular group of levels in World of Warcraft, then follow these tips about to where to level. This is a just a brief Horde leveling guide to help you if you're stuck running around trying to figure out where to go to grind experience points. This outlines where to find some of the Horde quests by level. For much more detailed information and step-by-step in-game walkthroughs, you will want to pick up Zygor's Horde Leveling Guide.
Now let's begin:
First, run through your starting zone to get to level 12. You'll find all kinds of quests and get through it in an hour or so. Next, head over to Crossroads, which is located in the Barrens. There are all kinds of quest chains to do here that will get you to level 20 quickly.
Once you hit level 20, make your way over to Stonetalon Mountains. The Horde town there has a bunch of quests that will lead you to areas in that zone and by doing each of them, they will get you to level 25 quickly.
Thousand Needles is across the Barrens, and has quests all over the place that will get you up to level 40 fast. Start off at the Horde town, and move through the quests to the west. Try and do them so you don't have to spend too much time back-tracking. It will allow you to level faster if you aren't running back and forth too much.
After you've done the different escort quests in the zone, head over to the salt flats. There's a variety of additional chains to do at the racetrack. And, once you've completed those, it's a quick run south into Tanaris, where you can quest up to level 45.
Some people like Hinterlands from level 40-45, and the area does have a lot of quests, so it is also a good place to knock over some levels fairly quickly. Then at Level 46 or so, head up to Felwood on Kalimdor. There's a ton of horde quests, and some rep you can grind while questing into Winterspring. Winterspring is the last place, and is loaded with quests that will easily get you to level 59.
For more hints and tips for leveling your Horde character, my review of Zygor's guides should get you going.

