As a Los Angeles native, my teams are the local teams. Lakers, Clippers, Dodgers, Angels, Raiders, Rams, Bruins, Trojans...in that order. In other words, I'll root for the Clippers as long as they're not playing the Lakers, who are my number one team. I never played hockey or soccer so I don't care much for either one but I do understand the basic rules and appreciate both sports. Many UCLA and USC fans have an intense hate for each other, but I'd rather see a team from nearby win than one from far away.
While I root for my own teams I am for the most part indifferent to other teams, and will even have favorite players on the teams I dislike the most. I am fan of basketball, baseball, and football first, my teams second. I always enjoy to watch highlights and will watch the playoffs and championship series regardless if my team is in it or not.
The teams which have caused me the most pain as a fan are: Celtics, Pistons, Suns, Giants, Padres, Patriots, Broncos, Chiefs, and Chargers--but I pretty much don't like every other team too.