Most commonly by the geographic area one lives in or has ties to. Otherwise, some people like to choose a team that wins a lot or, on the opposite side, an “underdog” team that never wins.
Yup, that’s me. I grew up near Seattle, so the Mariners and Seahawks are my teams for baseball and football. I got into soccer after I moved to Utah and the Sonics left Seattle, so Real Salt Lake and the Utah Jazz are my teams for soccer and basketball. We didn’t have a hockey team growing up, so I went for the Vancouver Canucks for hockey, but now I’m going for the Utah Hockey Club.
I used to really like the As because of Moneyball, and if I’m watching a game with other teams, I go for the underdogs (e.g. for the Premier League, anyone other than Man U, and I’m partial to Arsenol because they have a cool name).
Like a religion, or culture. As other have said, location, family, etc. Also, advertising plays a role, and then there are people who get really into it and spend a lot of time focusing on different teams, and sports, until they just become team/sport agnostic or focus on the one that meets their statistical, and business practices, requirements.
First step is to forgo a distinct personality.
Geolocation or affinity to location, significant player from region playing at team, family inherited “not ok to not like team xyz”, stats, position (underdog, champion) etc
In addition to the other reasons mentioned, I’ll add simply going to a home game for a specific team as an introduction to a sport. For example, I live in an area with multiple high level college sports teams. I went to my first college basketball game at age 11 at one of these schools, so I was their fan for a long time after that. Last year we went to visit the town where my wife’s dad is from. They have a professional team for a sport I enjoy but really only watch at the international level. I had no pro team I follow in that sport, but they were in playoffs while we were there. At that point we didn’t get tickets but I was watching on TV and I enjoyed watching, so I found a way to watch more at home. If we ever go back I’m pretty sure my wife’s cousin will get tickets so we can go. I did get a shirt for the team before we left.
