One of the great things about warlocks is that the playstyle changes a lot depending on your spec. I'm personally a big fan of affliction, so I can only really tell you about that part of it. Note: I'm a really big fan of affliction, so this became sort of long :P. Hope you can use it.
Affliction is absolutely awesome for solo grinding/farming, decent in 5-mans (it takes at least 30 secs for aff to get to full dps, so it's lacking on trash. Doesn't mean that it's bad though), and awesome in raids. IMO there's nothing out there that can beat it. You can dot a mob up, immediately target the next mob, dot that one up, next mob, etc., drain life as needed and remember to loot. It's only the mob spawning that will slow you down. With this build you'll be using the imp (on passive) or the felhunter (but needs the talent in aff to be effective). With dark pact you can steal their mana, and keep your own up almost indefinitely. Since your pet can't tank for you, you'll be taking the hits, but with haunt, siphon life and drain life this is a non-issue. There's very little that can't be drain-tanked (not including hard-hitting elites - don't forget where the summon voidwalker spell is).
One of the challenges as aff is to maintain the dot rotation on bosses. It is necessary to have a dottimer to do this. It will show you how much time there's left before the dot falls off. I recommend
DoTimer. I couldn't play a lock without it. Once you've learned to use it, the goal is to keep all your dots up at once, refreshing when they drop off (but only when they drop off, not before) and filling in with shadowbolts and life taps/dark pact.
A good dot rotation for bosses is shadowbolt, haunt, immolate (immo), unstable affliction (UA), curse of agony (CoA), corruption (corr) and maybe siphon life if there's a lot of AoE damage.
On trash mobs you'll have to learn to judge how many dots to put up. If it doesn't have a lot of hp, just use corr and shadowbolt. The more hp, the more dots you put up.
For soloing you'll want haunt, immo or UA, CoA, Siphon, corr. This will take any mob down quite fast, but if you have enough spellpower you can also just use the 3 instant dots, however, since the mobs in wotlk have more hp, I've found that it takes too long to kill them with just these. There's also the fact that you can only drag a mob so far before it evades and resets, and as aff you'll be running around a lot.
Hmm, what more. In instances, it's your duty to keep the healer soulstoned and provide the group with healthstones. It's best to throw a soulwell up before each boss.
As for your spec (haunt/ruin), it's not too bad, but I would make a few changes. Most important is dark pact. You cannot go this far into aff and not take it. It is a baseline talent for aff. I would also take the points out of malediction, at least for now. It might be very useful for raiding (depends on your raid composition), but it has no use anywhere else. In destro, take the points out of molten core. The only fire spell you'll be using is immolate, and the points are far better spent elsewhere. I'd suggest something like http://www.wowhead.com/?talent=IbxrbhMAoViocstZE00q with 2 points left over. It's good for soloing and 5-mans, and decent for raiding. Shadowburn is a neat spell for soloing.
The affliction build you posted is very close to the haunt/ruin one, my comments are the same as to that one.
As for gear. Stam, int and spirit is good (not sure if int is better than spirit now - it's been changed lately). Spellpower is your most important secondary stat, but only when levelling. When you reach lvl 80 hit becomes the most important stat; you'll want 157 for heroics and 447 for raids. Spellpower then becomes second in importance, and then comes haste and crit. As with int and spirit there's quite a bit of discussion about which is best, and I'm not sure myself. But take some of both once you're hitcapped and you'll do fine.
Edited, Dec 18th 2008 2:59am by KhamulDB