I recently lost an account because Blizzard mistakenly thought I was running a bot program when, in fact, I was playing in a scaled VNC window at 2 frames/sec. They wouldn’t listen and didn’t care, so I went and started a new account to try to regain my level 60 priest.
First time around it took about 5 months to get to 60 in casual playing. This time it took about 3 weeks of intensive leveling and I thought I would post what I did for others:
1. Do as many red quests as you possibly can. Don’t worry about the difficulty. Red quests done quickly give the best XP (sometimes 6000 or more).
2. Have a guildy or two help you blow through those red quests. The key here is fast.
3. Find areas that you can "grind" XP. This is the worst part. It is crucial that you do this alone, not in groups. No matter what anyone says, grinding alone gets you much more XP than any other method. I did this by turning off all sound in the game, throwing a good DVD or recorded TV show up on my second monitor and just runing around in about the same area killing as much and as fast as possible. Try to find that point at which you can continuously kill stuff without having to break for mana drinks or health regens.
I know this sounds boring, and it really is. I’ve read a lot of "1-60 in 2 days" posts that are simply false. I think this is the only real way of being able to get to 60 in any reasonable time. By the way, time played for my character when I hit 60 was about 12 game-days total.
From 50-60 my average xp/hr was about 22k and I did 1-2 levels a day easily.
I hope this helps!