Takes 1 day if you have any idea what youre doing at all and are good at your class. (and maybe have a friend keep you company).
see:
Opening Week Tier 6 Contest
I started 2 days after Zahr and Trauma did, just thought i'd point that out. Me and Grei leveled together and hit 70 in less than 24 hours.
To level quickly, it's probably best you have some experience playing the game. For best results, imo, do quests, lots of them (again it helps if you know where the quests are and how to do them). Good luck and I hope you enjoy your time here