Several things I do or don't do:

 - I have some specialized "expertise" in some areas, such as MySQL in Ubuntu (just one random example). Every now and then I do a search on the site when I feel like diving into MySQL again. Using Google gives me way more relevant search results.

 - I don't use tags because of the enormous amounts of noise. I feel that they don't work very well on Ask Ubuntu. See for example http://meta.askubuntu.com/questions/5697/can-we-please-disambiguate-or-discourage-the-mobile-tag

 - The "My Tags" page as Jorge proposed doesn't work for me. In theory this should work - but really, not for me, for several reasons. Lots of them are quite old (> 3 months), tagged erroneously, been-there-discarded-that (still popping up) and worst: *gone* because of just one upvoted nonsense answer.

 - "Scanning" - Just scanning the plain active list, opening 10+ could-be-interesting-questions in tabs in the background, scrolling quickly and watching for either "easy mistakes" I can easily answer, "interesting" within 3 seconds well written questions, "less than perfect answers to questions" such as https://askubuntu.com/questions/237077/does-12-04-lxde-have-lts and https://askubuntu.com/q/240160/88802 were. With already one answer with upvotes these were not showing up, yet interesting to answer.