First, its a ton easier leveling one character than multiboxing. There are quite a few 76s on my server already.

There is a really simple trick, beyond stuff like having 0 downtime, instance grinding, specing for fast kills, etc. DONT LOOT. You waste a ton of time looting. However, I think this is just dumb. I'd rather have all the gold, profession mats, etc and take an extra few days than to hit 80 first and sit around bored.

One of my guildies is 74 and he is a ret pally, he says they never loot anything except bosses and he is running in a group that is just grinding instances 18 hours a day (they are sleeping for 5-6, lol). That seems incredibly boring and a horrible way to experience WOTLK personally, but to each his own.