As Feral:
Open up with pounce, FF, mangle, shred, maim, shred, run and get distance while shifting into bear, feral charge, mangle, bash, shift to cat, shred, maim... then do what you need to do to finish them off. It's a pretty good stunlock pattern given that none of your stuns miss or are resisted. Use a pvp trinket if you need to, but the biggest downfall is a failed stun. An sl/sl lock would be the hardest to down but this is still your best bet.
As Balance:
Most of my experience is against sl/sl or felguard locks as those are the most common pvp specs. Either case, I kite the pet around in travel form while dotting with moonfire and IS, occasionally throw in a wrath or two. You kite in travel form so that the lock can't drain you. Once the pet is dead, you can kite the lock in travel form the same way. With no heals and no pet to take the dmg, they'll go down fast with dots on them. Sometimes they'll resummon the pet at the cost of a soulshard and you gotta do it all over again, but they typically can only do this once in a single fight.