Destruction Warlock revolves around direct damage with the rotation that closely resembles that of a Mage, in shorter fights it can deal more damage than Demonology and Affliction.

Rotation for Destruction Warlock Wotlk

Destruction Warlock Priorities

Curse of The Elements (If no other spell buff is present*) > Immolate > Curse of Doom (If there is a spell buff*) > Chaos Bolt > Conflagrate > Incinerate

Tips

The pet of choice is the Imp.

*Balance Druids and Unholy Death Knights can apply the bonus 13% spell damage if neither is present Curse of Elements is the best curse.

In a boss fight Curse of Doom or Curse of Agony end up neck to neck in terms of DPS, plus the 24 secs to 1 min will allow the use of extra Incinerate or refresh of other DOTs, so it can ease up the rotation and keep the DOT longer especially on the burn phase.

At the end of a cast, an instant spell can be cast without occurring GCD, this is true for every cast/instant sequence, should be used to maximize DPS.

Use CDs when there is barely any movement or crowd control effects to maximize DPS, the best way to do this is by knowing the fights and use gateways to minimize movement.