Picking what team you should root for can be chosen many different ways. You can like a team because your family does, because that team was good when you were little or cause you live there. I live in the middle of both New York and Boston. For me, I like the Celtics because when I was eight I saw the Celtics win the 07-08 championship with Ray Allen, Paul Pierce, and Kevin Garnett.
I went walking around my school to see what teachers and students said about who they liked and why. One of the answers I got was the Knicks and and when I asked why he said “When I was little I saw them win the 1970 and 1973 championships”. Another answer I got was the Celtics because his wife works for them. I asked some students too and they said because they also witnessed them won the '08 championship.
I Found that people also the Celtics only because they were doing a lot better than the other team. There people that didn't like the sport and only went for a certain team because of friends and family.