Okay, so this is my first guide. Didn't find any similar when searching and haven't copied this from anyone.
Requirements:A booster[Preferably AoE(Turn back at this point already, if you can't get one..)]RAF's available.
1. Send a RAF to your e-mail (Preferably not the same as your main account)
2. Create a trial account from the code you got in that e-mail.
3.Create a character you wanna lvl to yourself and any char to the RAF account.
4. Run the 2 clients. One for your account and one for the trial.
5. Now you just put another char on follow on the other and start doing quests like normally. Best place for horde are either Durotar, or crystalsong forest.
For allies the best place is clearly Azuremyst Isle.
Beginning for Horde:
Level your characters to 8 by questing. Now you can start running RFC with your booster. (You will get the best exp, if you only clear the troggs and then reset.) Run this untill you are 13-15.
Now you can start WC. Best exp is gained by running to the Lord Cobrahn, aggroing all the mobs on the way, then run back and pull all the raptors.
Run untill you are 17-20.
Now you can start running SFK. Just clear the whole instance and repeat.
For Allies:
Quest untill you hit lvl 13. Now start running Deadmines. Just do full clears doing as big pulls as possible. (Note that too big pulls can be dangerous for bad geared high lvl as many mobs can stun here).
Repeat untill 17-20
Now go to Stockades and pull the whole instance, AoE 'em if possible and repeat.
Both factions.
Now you should be lvl 20-25 and you can start running SM!(My favourite part)
Just enter the SM cath. Booster takes all the mobs from outside the cathedral and kills them. Now go inside, hit the boss (Mograine) and all the mobs inside the cathedral will come. Kill them and repeat untill lvl 40.
Now you can go ZF or ST. Just clear all mobs and bosses you want and repeat untill you are 45.
At 45 you can Either go to Scholomance, or Stratholme. Stratholme is my favourite. In scholo, you really can't AoE that much. In Stratholme, do not pull many crypt beasts at once, as they can cast you 5 second silence, which can be deadly. Clear both town and scarlet side.
Notes:
I did this with a lvl 80 naxx 25 geared holy priest. Best class is most likely paladin.
It is very adviseable to have booster a ressable class, as your alts will most likely die alot.
I have done both: Multiboxed 3 clients. Myself, RAF acc, and booster. and only 2; myself and RAF. In overall it doesn't matter that much.
In stratholme you better loot all the mobs; I've looted about 20 boe blues, Krol blade and Stockade pauldrons. Done about 5 runs. Also the righteous orbs still sell pretty well.
When killing Rivendare on stratholme, leave the alts outside the door. (inside the building ofc.) They will still get the exp and loot.
Well... That's about all for now. I hope it's not too confusing and that you like it.
EDIT: Well, yeah you can't go to azyremyst, or Eversong as trial.
Anyway as someone whined: "You can't pass lvl 20 as triall acc..." Well as RAF acc you can.
Ye, now I saw it's a repost and I apologise. Well, at least I've seemed to help few people.