Also: Make sure you are oiling the bobbin case(with the bobbin out) Take off your plate on the bottom and make sure there is not lots of lint built up under it.
Put your stitch length at 0 if you are FMQing.
I unthread and re-thread the entire thing if I'm having problems. make sure your thread isn't hung up on itself. With some threads, I use the hangy thread thing, even if it is not a large cone, just because it seems to make it easier.