What seems to work best for me is answering other peoples questions! Often that involves installing a module I've not used before and reading the documentation a little. That exposes me to new ways of doing things and new things to do.

Occasionally that even works in answering my own questions! In one or two cases the best answers I got (for me anyway - YMMV) I wrote myself after reading some initial relies. :-D Sometimes I go back and re-read them to remind myself how do solve a particular problem, or re-read snippets or CUFP's for the same reason. Super Search is a nice augmentation to the index I keep in my head.