Selecting which category of discussions you respond to.

Come to think of it, I actually do. I check discussions from my interests first and see if there's anything I can give input on. Next would be the discussions my friends have started. One of the good things there is that you'll find, at some point, that your friends have some interests that you haven't chosen yet but you have a common interest in. Then I go to headlines and see if I can comment on some especially if the news are a bit close to home. These are my preferences although rarely, I just post away to almost anything under the sun.