My algorithm is (notice new follower) -> (ignore). The thing I happen to like about Twitter is that it's curated. I've found plenty of interesting blog posts, videos, etc. by following a handful of people that interested me. Beyond that initial spike in follows when I first joined, I haven't actually followed someone because they started following me.

If I notice that someone is getting frequently RT'ed by some of the people I follow, and the original tweets are actually interesting to me, I start following them. I don't really use any other way of finding followers, and it's worked out fairly well for me. I have a fairly uncluttered twinbox, but I still get a healthy dose of interesting tweets.