You should follow liberally, of course, and unfollow liberally. I find it gratifying to "turn down the noise."
I liberally unfollow:
Hashtag soup
Un-annotated "follow" lists
People re-tooting their own content
Pictures of tweets intended to provoke disgust
I also filter these strings:
RT, twitter.com, wordle
What gets you to unfollow accounts?
@ambihelical Good question and no it didn't filter my own toot. And I wonder how many other like-minded curmudgeons will never see my toot! :D