I tend to identify stuff that needs work and schedule practice around that. It also depends on my tournament schedule, generally I put in more practice leading up to a tournament. These are the kinds of things I'll work on
Spares shooting at single pins
Looking at the effect of various adjustments (loft/hand position) on ball reaction, comparing multiple balls
Drills (foul-line/2-step drill)
Accuracy aiming for a specific target, usually, this will be some area of the lane where I'm less comfortable such as outside 5th board or inside 4th arrow.
If I'm leading up to a big tournament, I often go up and aim to just relax and get the ball off cleanly. I try not to focus on anything too major this close to an event, so maybe just some spare shooting and some repeating of shots, to keep the arm and body loose
--------------------
Reporting from England