I can't say that I've had any motivation to level a World of Warcraft character 20 levels in a day for any reason, but I've come across some serious addicts over six months of playing the game. Whatever the effect the game's had on them, some of these people have come up with some ingenious strategies to cut down on time developing their characters.

I was having trouble getting my priest leveled up in the Deathknell area, and I mentioned this to a hardcore player with over 50% of her achievements completed. She gave me some simple advice that, while I haven't followed it to a T, helped her develop five (!) level 20 toons in one day:

1. Reach Level 5 wherever you start out.
2. Take a zeppelin to Durotar and head south into Razor Hill. Start questing there.
3. Eventually your character will get nudged toward Sen'jin Village. Keep completing quests there, even grays, until you reach level 12.
4. You may need to grind a little in the Barrens before you reach Silverpine, but once you're around this level (you'll find what works by trial and error), level up to 20 here.

That's it. Some of the best secrets are the simplest. If you test this out, please let me know how it worked and what tweaks, if any, you made to improve it.