i have all classes except shaman, just level general profs dont need to level it all.

i usually lvl a new class becoz i have to company my recruit.my 85 druid exist becoz i did lvling wit my wife's mage.my poor lvl 40+ shaman & hunter becoz i lvled with my recruit until they stopped halfway playing

I have

5 alts and 1 main. Let me tell you , just go and put music and quest around. Its simple. You meet great people along the way. The two new alts I created were mainly because of RAF , so I just level till 31 and instant ding to 80 and then quest from 80 to 85.

Generally I do power leveling , I pick quests that gives me more xp and things like that and quickly switch. I don't bother leveling prof while questing as well.

I have alot of alt..first I start at Maiev, have almost all class except DK.
Then transfer to Thaurissan. Only bring my main. I create another  4 alt there. Fastest way to ding is to equip heirlooms and queue as tank or heal. Anyway queue as  tank will be much faster. If you are dps class only like rogue/mage/lock, set your heartstone to ogrimmar and check command board. If got quest to certain area for example Ashenvale , just go for it eventhough you think it was quite high for you.

My record for fastest ding to lvl 80 is 12 hours(play time) with my RAF friend. I queue as tank while he queue as healer. At lvl 70, i still have a few lvl 20 gear item.

There is a way , you need to RAF la

So what you do is level a new character with friend , do dungeons and quests and some group quests , you'll get tons of XP . You'll instantly ding faster not to mention with heirlooms. This will bring you and your friend roughly around 78-80. Now your friend can grant you a level for every 2 levels earned. So lets say you have another alt , get it to level 31 , then you can ask your friend to grant level to your other alt. This would birng both the characters to 80

I can provide you an addon which I use to level my paladin and my DK , without RAF. It helps me with which quests are worth it and which one should I ignore

my 1st toon was pally.no raf what so eva.lvl it the normal way to 80.when cata release i reroll DK ( becoz someone in my guild told me that pally ret was useless in wotlk raid and my guild was a PINKY RANGER GUILD)
i lvled my DK casually as a blood tank (love the tanking) i didnt do any quest for my dk.i spam dungeons all the way and i lvled my blacksmith and my enchanting without moving from thunder bluff (my pally was a chinese gold farmer) and thats how my DK became my main
i got 4 lvl85s.dk,pally,druid,priest.geared DK and pally only.priest and druid for profesions
planning to try Monk

scroll of ressurection poof 80 and 80-85 like a piece of cake

for fast lvling, you need heirloom gears, Guild Perks (Fast Track) and Recruit A Friend (RAF).

Nah..raf bonus only till 80. No more after that..Im doing questing with my RAF only now.

My Spriest, DK, Pally, Mage, Hunter, Warlock are all lvl 85.
All are ilvl 393 (except the lock which I levelled just past 1 week) and above.

The key to it is pretty easy, if you have interest in trying out different aspects of multiple classes and like to understand raid as a whole, then levelling them is a key thing you have in mind. I like to raid on different alts in order to understand better the roles and limitations.

An example would be clumping adds up in warmaster is so much better for a DK/rogue/warrior cleave and this would be oblivious to you if you just play a range caster. If the raid leader is not doing the right strat to augment your raid composition, you would be able to know as well and can tweak it with him. By adding this value, you can prove yourself to be an invaluable raider.

As for professions, never farm items. Always buy from AH, craft the items (boe), and sell back for a profit. Rinse and repeat. That is far better method. That way, you can have lotsa gold while getting your professions levelled. Also try to have professions that directly benefit your main toon's raiding. JC, enchanter, Alchemist are a must.