Post by Jidor
I've done some leveling up using guides here: http://wow-pro.com/
Jame is pretty much the top name in free guides(For paid guides, it's Joana and Kopp)
As far as I know there aren't any big annoying flashy ads, though they use google adsense so the words "Wow gold" may show on the side sometimes.
Post by 236yfpjkjhd
If you started in the Barrens, go Stonetalon Mountains after that. Lots of quests to do there. When you finish there, proceed to Thousand Needles. Also some stuff in Ashenvale, but that zone don't have that many Horde quests, and it's really big so there'll be quite a bit of running around.
Mostly you should go there to get the quests down into Blackfathom Deeps. There's a really nice caster staff to be had from the Orc boss towards the end, and the quest reward wand you get from turning in his head is the best you'll see for many levels.
When you get into your 30s you have tons of places to go. Stranglethorn of course, Desolace, Arathi Highlands, Swamp of Sorrows, Dustwallow Marsh, Southshore/Alterac Mountains, and so on. Late 30s, try Badlands as well.
40s you continue in these same zones as the higher level quests in them will give good exp even as you hit the low 40s and will be very easy to do due to mobs being "green" in level in many cases. Stranglethorn's large level range will also have much for you to do well into your 40s. LOTS of quests in Tanaris. You'll also gain access Burning Steppes and later on in your late 40s Azshara and Felwood. 50s, Un'Goro Crater, Blasted Lands, more Felwood (though not so many quests there, but you got Timbermaw rep to grind if nothing else). Western Plaguelands has a few quests to do, as do Burning Steppes. Eastern has lots, though many of the ones in these zones eventually end up in one of the old-world dungeons which no-one goes to anymore.
If you STILL haven't reached 58, or even 60 by now :-), there's also Silithus. Quite a bit to do there, many mobs there are very dangerous however and/or will bring hordes of adds if you're unlucky. Tread carefully if you solo it a lot.
For the easiest leveling possible for this class I suggest you spec Affliction. Apply your shadow-based DoTs, then drain life on the mobs. Lifetap to restore mana, drain more life etc. :-) Harder mobs you can Immolate too for some extra DoT power. When you get into a steady routine and have learned how to use your skills to their full effectiveness you'll finish almost every fight with both full health and mana. When your demon needs a refill you just Life Funnel it - with talent it'll be a very minor dent in your own health, and in dungeons you'll use Imp constantly set in Phase Shift mode and drain his mana to top up your own.
When you reach high levels you can start putting points into demonology for more stamina and intellect etc until you get Demonic Aegis. Check this strong affliction build which I use on my undead lock: http://www.wowhead.com/?talent=IEMrioctVt0o0gc0c
You even get three leftover points, which you can put either in Improved Blueberry or Succy, or Fel Stamina, depending on your mood. :-) Or you spec Grim Reach and get a leftover point which you can put in Curse of Exhaustion for more PvP fun. :-), If you feel brave/extra evil, you DoT up a whole bunch of mobs and then use your Improved Howl of Terror to fear them all away at once. Curse of Exhaustion is also useful here and will stop them from running for help/bringing adds.
Do note, Succy can't tank your damage output even if you put points into Improved Succy, so you'll need to draintank the mob yourself if you choose to play with her. Towards the upper levels, un-improved Blueberry usually holds the mob until it reaches about 30% health, and if you have Grim Reach it'll likely die before reaching you. If you haven't, you get one or two whacks yourself before the mob dies, damage which you'll likely heal back through your drain spells.
Very effective. :-)