I'm leveling destruction, and I find that it is quite fun. It's also killer for pvp. Skip Cataclysm (Waste of 5 points) and grab Improved Shadow Bolt. Aftermath *can* be useful in pvp, but not so much in pve -- I just went with Bane (good to get anyway. Cast shadow bolt faster? Yes please). I hear that improved firebolt is bugged and putting more than 1 point in it is a waste, but don't quote me on that. Some of the more experienced locks might be able to answer on that. Devastation is, of course, wonderful. More crit = more damage = kill things faster = less mana spent = less downtime. Just be warned that you will likely rip aggro from your pet (Even Big Blue) almost every time. Shadowburn is an excellent finisher that pays for the shard it uses if you kill something worth experience. Destructive Reach is great for pvp (and probably handy in pve too). Anyway, that should get you started. I believe there are some destro builds for the higher levels posted in the stickies.
EDIT: Oh, regardless, you want 5/5 Faster Corruption. Instant DoTs are very important, even if you aren't affliction (Especially in pvp).
EDIT: Also, invest in some food/drink. Destro is much more mana intensive without the life tap/drain life combo that affliction gets (or rather, the more effective version they get with talents ;) ).
Edited, Apr 24th 2008 1:12pm by Phelios
Edited, Apr 24th 2008 2:33pm by Phelios