I have found it's a good idea to take stock of how the tweets of the people I follow make me feel. When I was new I would follow anyone funny, and I pretty much give everyone a chance and follow anyone who follows me.(except spam of course)
Eventually I learned one person who seemed funny at first was always posting something horrible or negative. There were even short sentences like "why do I bother", She could not be consoled and would invariably wind up saying she had to log off because she was so upset. Even though I didn't think this person was evil I eventually unfollowed because I found myself very tense over her dramatic negative tweets. There were also people I liked who turned out to fight with strangers. yes, fighting with strangers on the internet about a scripted reality show. You've seen it too probably.
In real life we can't always control who is in our lives but on twitter, the experience is truly what we make of it. I have learned to weed out negativity. I enjoy knowing that each person I follow is someone I can respect and truly wish well. Anyone else, it's aloha on the steel guitar even if we have a mutual follower. Happy tweeting all.