I've found it best to do:
VE (optional) > DP > VT > SW:P > MB > MF > SW:P (since now you'll have 5 SW stacks) > SW

I also have a mod called ShadowGreenLight that helps letting me know when to put up a new SW:P.
I use that rotation because MB and MF do additional damage with SW:P up. I also keep an eye out for when Dying Curse procs so I can refresh my SW:P.
Sadly, Blizzard fixed the bug that allowed Mind Flay to apply 2 stacks of SW instantly, but oh well.
That's my boss/Ulduar non-AoE trash rotation, and I pull roughly 3400 DPS which I know could be better. I actually think damage is more important than DPS, but each to their own.
Let me know if anyone has a better rotation I could use to up my DPS.
ALSO, all shadow priests should really get ShadowGreenLight. It keeps track of your SW stacks, Imp Scorch, and other class spells which benefit your damage as well.
Edit: My priest's name is Healzfound now after a realm transfer. Gotta love the irony
