Have you used a Horde leveling guide before? If you're leveling up a new character this is the best helper you could get to reach level 85 in the shortest time possible.
I started to use a Horde leveling guide after I took my second character to the level cap. I really don't want to bother too much with questing and with the whole leveling process and the best shortcut seemed to be a Horde leveling guide.
Anyway, what made me write this post was to provide Horde players with a general leveling path from 30 to 40. So, here's a short Horde leveling guide 30-40.
For 30-34 you basically have 2 alternatives. You either choose Cape of Stranglethorn or the Hinterlands. But unless you really want to spend some time in the southern part of Stranglethorn Vale, and complete some quests in Booty Bay, I strongly recommend to go for The Hinterlands. This zone is closer to the next zones. So, after reaching 34 you won't have to travel much.
By the way, I forgot to mention, the guide I've been following is Zygor's Horde leveling guide.
So, the most important quest hubs this guide has pointed out for me in Hinterlands are: Hiri'Watha Research Station and Revantusk Village. Once you complete the quest here, you should be level 34.
Once you hit level 34, this Horde leveling guide will take you to Western Plaguelands. There are plenty of quest hubs here.
Since you're coming from Hinterlands, you should start with Andorhal. Then you will be sent to the Bulwark and after that to the neutral camp - The Menders' Stead. There are quite a few flight paths now here, and this facilitates your moves in this zone by a lot. In fact, you'll be passing from 34 to 39 in two, maximum three hours.
And, of course, the last level in this Horde leveling guide 30-40 should be in Eastern Plaguelands. If you don't reach level 40 by doing the quests at Thondroril River, the entry point to EP, you should be 40 for sure, by the time you reach the Crown Guard Tower.
I hope this general Horde leveling path will give you a little orientation if you don't follow a Horde leveling guide. If you want to buy a complete guide, I can only recommend Zygor's Horde leveling guide. It's the best at the moment, but to see for yourself, you should check out a few Horde leveling guide reviews.