Your character in tip top shape for WOW power leveling include:
1) Keep Your Character Geared
Keep your character geared or at least somewhat geared. Again a bit of gold helps here. It wont be so easy in the beginning but as you level up past 20 or so you should have a decent set of blues from doing instances. You never really want to be running around with gear that is over 10 lvls “old.” So keep an eye on that. If you are leveling fast enough this can happen before you realize it.
2) Get Heirloom Items For Your Character If You Can
If you have a character already at level 90 then farm the badges to buy Heirloom gear for your alts. The most important items are the chest piece and the shoulder each of which will give you the 10% extra experience which will stack with each other to give you a 20% XP total boost. The other items such as weapons etc give you a great item to level with that is superior to anything you’ll find in dungeons out there.
3) Use Enchants/Gems To Your Advantage
If you have any gold I would go as far to enchant whatever items you can as well. Once you get to level 60 or so you will get empty gem slots in some of the gear you get from quests and instances. My best recommendation for these slots is to always have them filled. These slots are there to help you enhance your stats which allows you to get though quests faster etc. Furthermore, don’t bother with burning crusade gems, shoot for the “green” low level Northrend gems.
4) Keep Your Bags Empty
If you are interested in earning as much gold as possible while you are power leveling then keep emptying your bags every chance you get. This way you avoid having to drop drop things and lose the potential profit from them. Treat going back to town as a way to refresh and make sure you have everything you need and bags empty before you go back out into the field to level. You don’t want to have to travel so much as it wastes a lot of time. Some things you come across will be great to sell, other things will help you level up a profession later and save you gold. Create a bank alt or two to mail things to if necessary.
If you have gold, buy the biggest bags or get them made by a friend. As you level quest items that you will need will be taking up quite a bit of bag space especially if you jump around to different leveling areas a lot.