What I like doing when I get the chance is practice my missed shots. I open my little book I keep and shoot them until I have a high success rate at that particular shot.
The book I keep I record all the runouts and greatshots as well as the misses. Don't want it to bum me out too much!
If I have been a little lax lately in my log I usually start with Brainwash (or dynomite as some call it.) Spread all 15 balls around the table at least 6 inches apart and at least 6 inches from the rails randomly. Take ball in hand run out all 15 balls. But! The cue cannot touch a rail or another ball. No combos, caroms, banks, or kisses. Just position from each individual shot.
I do about 3 racks. Average about 11-12 balls made. My personal best was two tables cleared back to back. This is my favorite.
Then I'll do a draw drill, and a follow drill to dial in my speed. Then I practice specialty shots. Jumps, combos, kisses, banks and caroms. (One rack of each.)
At any time I start to lose focus in these drills I stop them and just start playing straight pool against myself.
On a side note... some buddies and I got into a discussion concerning breakouts or tearouts of clusters if you will. We set up random clusters with a breakout ball in place then we had to predict as close as we could the resulting positions of the balls. Everyone soon found out we couldnt predict so well. (At least 3 ball clusters or more.)
This all came after someone commented on Reyes practicing this very same thing himself before a tourny. It's humbling and worthy practice.