You really just go by zones. Through questing the game will guide you to chains within zones that are level appropriate for you. Also depends on if you're horde or alliance.Care to give some examples of those epic quest chains? I don't mind spoiling myself since I want my experience in WoW as entertaining as possible.
For alliance, I remember loving both Eastern and Western Plaguelands, Blasted Lands, Redridge, Stranglethorn Vale, Duskwood, Darkshore and Westfall. And those are just off the top of my head, probably forgetting some.
60-70 is Outlands and isn't all that great to be honest. I just trying to get to 68 as quickly as possible through dungeons and some quests so that I can go to Northrend.
Nothrend will last you from 68 to 80 and is a massive improvement over Outlands with some amazing questlines. Howling Fjord is the best starter zone there in my opinion, then after that Grizzly Hills and Dragonblight. For your last zone you have either Icecrown or Storm Peaks. Both are great so you can't go wrong.
At 80 most people would say Mount Hyjal, though I like Vashj'ir. But either is good. And then you don't really have choices until you go to Pandaria at 85 and all those zones are good so it doesn't really matter.