I work on fundamentals, timing and a smooth swing. Often, I'll roll a few games using only my spare ball (polyester with pancake core) and will focus on smooth, forward roll and squaring up my shot to the pocket. Then, I'll work a few games with my spare +1 ball (mildest reactive), continuing to square up the shot. This usually puts me back on the right track. YMMV...

I bowl in the dark.

Slow down, fundamentals, balance. Generally, if I can just focus on ONE thing, then the other things will often fall into place. (This is much easier said than done, of course.) Anyway, for me when I'm slumping it often manifests itself in bad balance at the line, so the ONE THING I try to do is stay balanced on my slide. Just focusing only on my slide helps me in other areas without thinking about it as my muscle memory takes over the other things. Suddenly my swing becomes manageable, my tempo falls into place, my release point becomes consistent, my tilt aligns itself properly, and the pins just start falling easier.