Well.....
UA will always be better than ruin, at least until you have a sh*tload of crit and spell damage, and even then UA is much better on boss fights.
And Bane is a MUST if you have more than 5 points into destruction. Aftermath is just terrible, and really only suits a VERY heavy Destruction warlock. Even then, it's pretty bad especially when you have Curse of Exhaustion.
So, take Bane, get rid of Aftermath. I'd recomend getting iHoT, Contagion, UA and skipping ruin, but that's personal preference.
Back to the question....
While soloing you will want to drop Immolate>Corruption>Curse>Siphon Life and then Drain Tank.
If you want to use your Void, skip Immolate. Just do Corruption>Curse>Siphon Life. Then Life tap and drain tank to full health. Repeat the tap>drain step until dead.
While grouping it'll be fairly simple. On short fights, drop immolate, corruption, curse of choice on every mob except the ones that are CC'd or not being offtanked, and spam shadow bolt.
On long fights and bosses, drop immolate, corruption, amp'd curse of doom, siphon life, and spam shadow bolt. Renew DoTs when necessary, and replace CoD with CoA after it goes off.
Raids are a different beast that I cannot advise you on right now. Just 5-mans, soloing and PvP.
Edited, May 11th 2007 6:57pm by FieryCougar