Or, learn from my fail: a printable checklist (below).
I did pretty well really, over the last few lulls. It was only number three that I really failed at. Spectacularly.

Print off copies of the checklist and jot specifics you think of when you are too busy working, so that you’ll remember what you want to learn, do, and explore when you finally have the time.
Photo by JD Hancock used under CC BY-2.0 license. Originally published in my How To column at [the now defunct] Copyediting.com.
Checklist for a Work Lull by Adrienne Montgomerie is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.