How do you discover good/interesting questions quickly and efficiently to answer?
RSS feeds in conjunction with Notifixlite to get IM notifications on feed updates. I usually subscribe to the tag feeds of feeds I like, care about (like RSS :D)
I tend to pick categories that I have the most experience in and seek out the newest questions there. I like to take my time answering, and even then I go back and revise my answer on an average of 3 times just because I want it to be a good answer.
I'm not always the fastest to answer, but that's not what SO is about. It is about providing the best answer.
I use StackGuru to store my preferred tags and have the questions delivered to my IM soon as they get posted.