Here's some information copied shamelessly from Wowwiki on the various ways of getting into the floating city if you haven't yet.
Getting to Dalaran
There are several ways to get to Dalaran:
Dalaran Specific Methods:
- Mages can talk to NPCs in Dragonblight and learn to teleport to Dalaran after completing
[73] Attunement to Dalaran available at level 71 - Mages can learn a portal to Dalaran at 74 from the portal trainer. This allows anyone to get to Dalaran
- Anyone who is at least level 74 can complete
[74] The Magical Kingdom of Dalaran from any of several members of the Kirin Tor, which will portal them to Dalaran once - A set of crystals (Teleport to Violet Stand Crystal and Teleport to Dalaran Crystal) can be used, but the Teleport to Violet Stand Crystal must be used first, meaning that you have to have arrived in Dalaran previously (via the quest at 74 or via a Mage portal or a Warlock summon), the quest
[74] Learning to Leave and Return: the Magical Way provides XP and monetary reward for using both crystals (but requires level 70) - 2 rings are available at 80 (Band of the Kirin Tor, Signet of the Kirin Tor) which teleport the player to Dalaran
- Learn Cold Weather Flying, and fly there with a flying mount
Non-dalaran specific methods of getting to Dalaran:
- Once in Dalaran, players can set a Dalaran inn as their home, which enables them to teleport there with their Hearthstone
- A Warlock in Dalaran can summon players to Dalaran, with 2 others in Dalaran in the same group
- Dalaran has a summoning stone available for players who are eligible to enter the dungeons there [citation needed]
- Someone already in Dalaran can group-invite you for PvP at the city's Battlemasters. After you leave the battleground you will spawn in the floating city. However, the inviting player has to be of the same level range for the specific battleground pool as you, or you won't get to join the battleground
- After meeting the Dalaran Flight master (in Krasus' Landing), players can pay to fly there from nearby flight masters, via a Flight Path