Yo, what healer do you usually play with?
In general there is no 100% strategy to follow, since this is PVP, not PVE - your opponents will have different playstyles and you should expect so.
My advice is to try to avoid CC using your CDs and interrupts offensively, to stick on your intended target as much as possible. Between Lichborne, AMS, IBF, Strangulate, Mind Freeze and trinket included, you should be able to force at least mages/dpriests/spriests defensive or even go for the early kill.
Hpal/Awarr - warrior if too extended, if not usually swap to hpal whenever you find the chance. Force bubble, rinse and repeat. Kiting warrior is better than tanking and death striking. Can't say much here, good ones are too hard, less experienced ones are too easy.
Rdruid/Awarr - I like to stick on the rdruid
Dpriest/Spriest Rogue - avoid CC, stick on the priest. Don't be afraid to use CDs!
Rdruid/Rogue - I like to stick on the rdruid
Fdruid/Rogue - Cheese comp. If they are geared and you aren't as geared/countergearing it's hard. Haven't met many, I usually peel until feral dies. If they go on you just hope you got enough resilience, HP and frost presence to last.
Other comps I dislike as DK are good Feral Disc/Hunter Disc.
Anyway, just keep practisising and you'll get better and more comfortable!