So a few days after The Burning Crusade came out we went through all the new end-game content in an effort to prepare ourselves and our guildies for the upcoming attunement grind. We knew it would be hard, having experienced endless Jailbreaks and UBRS runs, but we didn't expect that we would have sit down and create a flow chart of the instances in order to even begin to comprehend the convoluted, overlapping, intricate Rubik’s Cube of pre-quests, key chains and attunement runs.
So after we did all that work, we decided it wasn't doing anyone any good buried in our computer somewhere, and decided to share. So here you go: the basic steps every player needs to follow in order to get attuned.
Nope, the first instance you should run in order to be prepared is at level 65+, Sethekk Halls in Auchindon, Terokkar Forest. The last boss drops the key to the Shadow Labyrinth, which comes into play later. It can be hard at 65, but can be done.
At 66 head out to Tanaris and the Caverns of Time (it's the big area that used to be off limits). Talk to the dragon at the top, fly down, do the tour quest (and if you are the only one in your group who needs it, arrive ahead of time so we don't have to stand around for fifteen minutes while you walk in a large circle listening to whispers). After the tour quest, run in and do Escape from Durnholde. At 66 it can be difficult, so make sure you go in with plenty of in-combat crowd control and a strong healer. Why go all the way out to Tanaris at 66 you ask? What fabulous prize is there at the end? Nothing, really, except eventually you want to get into The Black Morass, and you can’t do that until you’ve done Durnholde.
So now you have two levels to grind out the reputation you're going to need. Hitting 70 with the four main factions at honored is not a bad idea, and getting revered as soon as you can, even better. The four factions you should focus on are Lower City (Auchindon), Honor Hold/Thrallmar (PvP will get you rep when quests run out and you're still too little for Shattered Halls), Cenarion Expedition (by far the easiest) and Sha'tar (Tempest Keep instances mostly, hard to get any rep with them until 70). Long term, you'll need revered with Keepers of Time as well. Most factions stop giving rep gains about halfway through honored for anything except turn-ins and runs of their respective 70 instance.