Your biggest time saver is a mule character. (This is just a level 1 character that you put inside the main city that has both an Auction House and a Mailbox). Simply put, a mule runs back and forth between the Auction House and your mailbox. This character acts as a middle man between your main character and every selling option. This gives you an unlimited amount of item slots.When you are out questing or grinding and your backpack fills up, you will mail everything to your mule. (Except for items you would usually vendor, just vendor those.)
You can leave everything in the mailbox (this is what I do). This way when you need something like extra cloth for bandages, you simply log onto your mule character, open the mail and hit “Return” it send it back to your main character INSTANTLY! Don't worry about forgetting about items in the mailbox, if the timer runs out, it will automatically send it back to your main character.
Use your mule to buy and sell everything on the Auction House and to refill your main with any goods he might need. Try using Ctmod's Mail Mod to make this quicker. Get more exclusive insider WoW speed leveling tips from the Warcraft Pros
