I can only answer this based on what I did.

After college I joined the Army. it is easier to meet people in the Army than it is in college. The army was wild. The days last forever but the weeks go by quick. In the army it is not uncommon to meet someone and by the end of the day they are the best friend you ever had and two weeks later you don’t see them again.

After the Army I settled in a suburban area started working a civilian job and raised my family. I met my best friend as he lived two doors down from us and his two kids were one year younger and one year older than my kid, so we were the two dads watching over the kids in the neighborhood.

From there we started lifting weights together, taking our families to football games and having cookouts together. We also had other families in the neighborhood come and go.

I also made friends through work. I worked in IT so it was a fun job and the people I worked with were great.

The most important thing is proximity.