The best way to make a good use of unstructured time that I've ever found is to optimize towards highest utility. In plain terms, you have an ultimate goal, a be-all-end-all reason to be doing something, and you're doing your best to achieve this goal as efficiently as possible because each time-unit of delay is negative utility.

This takes a goal, of course, which is pretty much comparable to Step 7 of 11 For Building a Goedel Machine, if you've seen Eliezer's Summit presentation that touched that subject.