I keep a list of people who I know are well connected and either post high quality content or retweet it, so I get broad coverage of the communities I’m interested in. Unfortunately even the best accounts get caught up in the worst of a Twitter sometimes, but it’s rare, I’ve trained myself to ignore it, and by not having an account I can’t really interact with the people anyways so I don’t get involved in it myself. (Occasionally I do send out emails in response to people’s tweets, and in one case I wrote a blog post that I doubt was ever seen by the person whose tweet prompted it.)