Once again, as soon as you hit 70 - I recommend to go and learn faster flying. This speeds up your questing A LOT, and is worth the time and gold. It will cost 4500 if you go to the capitol, or 5000 if you prefer Shattrath/Dalaran, because you will not have reputation with them at that point. This price will sadly be above what a totally new character can afford, if you don't have any Main. But you should go and buy flying as soon as you have enough money.
BUT NOW, all the mobs except for the odd rare or boss in a zone are always the same level as you. Every combat is exactly the same. Aggro a bad guy, he runs at you, you go through your standard spell rotation; hit 3, then 1, then 3, then 7, then 3, then 4, then 3, then 3. Then you loot the corpse. It doesnt matter what you are fighting, every combat becomes EXACTLY the same. Boring. Pointless. Meaningless. And then when you complete a level and ding? Every one of your 30,000 enemies dings at the same time and combat stays exactly the same! You gain NOTHING from leveling. It goes from exhilarating to depressing. Why even have different mobs if they will be exactly the same? The could all just be a white blob. Heck, why even have the monitor on, just blank the screen and type 3-1-3-7-3-4-3-3. You could run it on a 70's programmable calculator. Start program, type "31373433" and look at the display for what random percentage of health you have left. Repeat. Again. Again. Again.

Also get the Heirloom Mount. Being able to have basic riding speed from the beginning will save you a lot of time if you're starting from level 1. Allied races start at 20, so this is a non-issue for them. It's important to note that Pandaren can not use this mount until they finish their starting zone and pick a faction. Being Horde or Alliance is a requirement of the mount.
The Alliance are able to unlock the void elves (exiled blood elves who can tap into shadow magic, trained by Alleria Windrunner after her experiences on Argus), Lightforged draenei (draenei members of the Army of the Light who fought the Legion on Argus), Dark Iron dwarves (fire-blooded cousins of the in-game dwarves of Ironforge), and Kul Tiran humans (larger, more heavyset versions of the in-game humans of Stormwind).[6]
The upcoming raid, Battle of Dazar’Alor, tackles this problem by having the Horde and Alliance have two raid stories — and the opposite faction will temporary flip sides for flashbacks that show the whole story. The Alliance storm the Zandalar capital and gain a massive upper hand in the war. From there, the writers will have to balance a compelling Alliance story with the rising threat of the Old Gods (and, of course, the ongoing Horde story.)