I played guitar in high school, I had friends in both bands I played with. I played hackie sack every lunch and before class in high school so I had friends from that group. I took 2 years of vocation classes (automotive) so I had friends from that group. Pretty much my advice is do things you like and you’ll meet people with a common interest and eventually make friends. Even as an adult, I go to cars and coffee every other Saturday in my town and after a while we formed a loose group where we caravan together to other shows in other towns.