Join a Community Band

 It's important to play with other people, as that's more or less what music is. If you're not playing with other people it can be of great determent to your sense of time and your tuning if you go long periods of time without playing with others. Your ability to tune relatively with the other parts will blur and your sense of group time will get fuzzy.
There's a lot of reasons for not having people to play with, Maybe you've just moved and you hardly know anyone. Maybe you've just started playing and have yet to join your first ensemble. It could be that you're just coming back to your love of music after years away due to your (misguided?) pursuit of fame, fortune, or financial stability. What ever the case may be, my advise to you is to join a community group. Why? Because community groups are typically filled with three types of people (and these types aren't intended to be exhaustive) from whom you can learn and with whom you can enjoy music.

The first type are old timers, these guys have been playing music in your community for the better part of their lives. They don't want to make any money off their music, they just do it for fun and they want you to have as much fun as they do. These people (depending on where you live) will know your father, and all of the kids in your community too, and as such can tell you a lot about who is playing music and where a lot of good opportunities exist. Treat these people well, because they are the reason that there is a music community where you live in the first place.

The second type are school kids. These people come from junior high school all the way up to masters students. They're either there because their mom makes them, or because they are considering, in one way or another, playing music more seriously than the average Joe. You should get to know these people well because they're walking in the same shoes that you are, and they are the forth coming musicians, the heavy players and high school band teachers of tomorrow. If you plan on living where you're living now for some time, you're bound to get to know these people quite well, so now's the time to start working on the lifelong friendship.

The last group of people are the pros. A good musician is someone who likes music, and is dedicated to making to with other people who feel the same way. Chances are the pros got their start in a community band, just like you are now. What's more is that they stuck with that band, or at the very least sit in from time to time. It's a great chance to meet these people, play with them, and see how the operate within the community. Maybe they're very gracious and grateful for what some of the old timers did for them back in the day, that's not such a bad trait to pick up. Maybe since they've hit it big they've become self important, and they just stop in to wow everyone. It's a good chance to learn how not to behave.

There's more to community bands that you can learn from though, like how instructive playing with strangers is, or learning a new sort of repertoire that you wouldn't have otherwise, or testing your own dedication to music by playing with a group that, at times, will test your patience. In the end music is music... you can't fail by becoming more involved.