Playing with Rest XP

For WOW power leveling, Quest is faster than grinding, you'll level twice as fast by questing, but you need to have your quest organized. That's why many players like a WOW Leveling guide by side. Those players have gone through leveling several characters all the way may not want it. After you've done the quests, make sure you have rest XP available when playing your toon.

If you run out of rest XP, hand in whatever quests and log out in an inn to recharge it.
If you run out of rest XP, and have to go on playing, then farm items, WOW gold, rep, or go kill other players. So, log into your bank and do some buying and selling.
If you stick to the rest XP, as well as having your quests organized, you will find yourself handling WOW leveling very well and leveling quickly.

Combine playing

Play several toons and combine playing them with the rest XP, when you have lots of playing time. When one of the toon is out of rest XP, log out and log in another toon to play. So you'll have two more characters do the WOW power leveling at pretty much the same rate. You'll be able to stay in the rest xp zone for 100% of your playing time, and you'll have all of your characters all hitting 70 around the same time.

Playing together with someone to do World of Warcraft power leveling, you will have your character goes by significantly faster. You will get less XP per kill, and you will kill things much faster. You will have less downtime, even if the extent of your healing capability is your first aid skill. Playing together, you can take on tougher mobs, silver elites and WOW gold elites will be much easier as well as team quests. And better chances of successfully ganking others.