I used to just throw everything at a target and then refresh all the dots when I got to the end of the rotation, but to be honest my DPS was crap.
I did a bit of research on Warlock's Den, and with a bit of a talent reshuffle, and a new rotation, my DPS was more often than not top of recount for the Kara + ZA bosses we were doing, even with much better geared destro locks in the group.
Talents. This is an all out boss killing DPS spec, so you lose practically all the utility spells you'd use for levelling, and have to rely on the fact that you're maintaining haunt above all other spells to keep your health up. It seems to do a much better job at this than drain life did, even with the talent and full DoTs on. (Spec has no grim reach, as it's no use when you still need SBs to be in range. No imp. felhunter, as it just kept dying from boss AoE, leaving me without mana, even though it's own DPS was a nice addition to my own. Only 2pts in Eradication, because the 3rd has a
much smaller gain then the first 2, due to an internal timer limiting the number of procs).
Glyphs were Corruption and SB, for maximising SB damage/minimising it's mana use (a very big part of the damage %, as nightfall procs a lot with corruption on all the time).
My opening rotation was Haunt > CoA > Cor > UA. They're in that order (decreasing order of DoT running time) to make sure they end as close together as possible, that way you get the longest window for spamming SBs (or Haunt instead of a SB when it needs it). Once they're up you try and keep CoA and UA up as much as possible, but Haunt is your priority, as it gives everything else that nice 20% bonus, and refreshes the Corruption. I try and fit the odd life tap in before a huant returns, so I always keep a bit of mana in the imp.
I used the DotTimer addon with 5 big icons for the spells in my rotation, in fixed positions on the screen under the target frame, so I could instantly see what running time was left on each spell, and how much cooldown was left on the haunt (the 5th icon). Trying to keep track of my own spell icons on a target among everyone else's, and with them moving around as things were added/removed was too difficult, so I went for DotTimer so I could keep a better eye on what needed refeshing (even though it was a pain to set up 5x fixed icons), and it drastically increased my DPS once I'd got the hang of shuffling the numbers in my head to work out what needed casting next, as there was next to no downtime on the DoTs, and I could start casting Haunt/UA when they had 1.5s remaining.
This could probably be tweaked further, and I'm not sure how well it works past L70 (I've gone back to a grinding spec with more utility spells), but I was very impressed with the sustained DPS I was doing to bosses, compared to everyone else in the raid, despite my gear being nowhere near as good (no tailoring set, which is best for aff., and only kara gear, when most of the others had some SSC stuff).
Oh, and make sure you get Omen, and drop the threshold to 85%. You can cause a lot of threat too ;)