In my spare time I speed run video games. For example, I can speed run the original Legend of Zelda in under 40 mins. (3 mins from world record... grr!) I've applied some of my crazyness to WoW. Here's my tips for specs.
Druid Tips:
10-20
-Start with 1 pt nature's grasp, then get reduced wrath cast time, then back to nature's grasp.
-Don't forget to buy water!
-If you can get a blacksmith to put a counterweight on something, then go feral instead. It will work in Bear form @ lvl 10 and greatly increase your attack speed. Haste is worth a lot at low levels.
Two options are rougly the same depending on your gear/preference:
Option 1)
20-35 - Feral
35-50 - Get Furor, Omen of Clarity, Natural Shapeshifter, and continue with Feral talents.
-Why OOC over LotP? Your crit rate is just too low to consider LotP as a worthy addition. OOC Procs will seal grinding speed, as your damage will most likely be capped by the speed of your energy regen. Furor will allow you to powershift to get quick kills.
Option 2)
20-40 Feral
40-50 Moonkin!
-Moonkin @ 40 can AoE grind mobs. I wouldn't recommend doing it for a pure EXP perspective now that quests are good- but if you have a bunch of multimob quests, it's superior to Option #1 for lvling speed. Simply run around and moonfire & insect swarm 3-5 mobs while in caster/travel form->let them come to you. Then Moonkin->Barkskin->Hurricane.
-Only do this if you've managed to get some +int/stam leather.. note: LEATHER. not cloth. You need the armor bonus to AoE.
Both options are superior to just going pure feral alone.
50-70
-Feral + Mangle. No question.
Paladin Tips:
Prot IS superior to Ret assuming you can twink yourself out with a shield spike and whatnot.
10-35 - Ret
35-50 - Prot
-Scarlet Monestary, Uldamon, Maraudon... If you have rest exp this place is nice to run. As a paladin you can AoE pull mostly everything with ease assuming your team knows how to handle a pally tank.
-Stranglethorn kill quests are easy. You can pull a whole troll camp. Or 5 Tigers.
50-60 - Ret
-Mobs are getting into the realm where they start doing more magic damage. Ret is superior now.
60-70 - Ret OR Prot
-Depending on how many instances you run, and given the speed at which instances are done with a pally tank, either is desirable. Though, if you're solo, Ret is the better choice. If you've done them before, you can be very precise with your Outlands quests and kill your 1 named quest mob quickly. Prot tends to take longer, but you end up getting experience for taking out the whole fort along with the named quest mob. It's a tossup. I personally have done Ret from 60 onwards.
Mage Tips:
10-30 - Fire
-Very easy answer to why fire is superior in early levels: You get your next rank 2 levels earlier
30-50 - Frost
-AoE grinding is mostly dead. But, theres still so much opportunities to AoE grind quests.
50-70 - Fire
-Easier to solo single mob quests that litter this level range. Blast Wave/Dragon's Breath becomes superior to Blizzard in AoE Quest grinding situations.