When did you last find yourself wishing that you could be a part of a group, whether it be sports, religious, community, professional or some other kind? It could be daunting to try to find not only a group that follows what you are looking for concerning fulfillment but also in camaraderie and atmosphere. The first step is to get out there and find them and then try them out until you have found one that fits.
Sports leagues
You're taking the kids to their respective activities and get started thinking about what it was like when you played as a kid. Then you realize that you haven't honestly played anything for years and all of a sudden have a strong desire to rectify that great wrong. Where do you start? Depending on what sport you are pursuing you could go to the local park and find a pick-up game—soccer, basketball, etc.—that might be just the thing to get you started. Or, you may decide that you really want something a little more structured that you can be a part of longer-term. Your answer may well lie in your local adult league. These leagues are wide-ranging in both the sports and the skill levels that they represent. Some ways to find these leagues are to do an internet search for “adult [sport] leagues [your area/city/state],” check with your local YMCA, find your city recreation center or maybe ask the players at the park what leagues that they know about. In that last case, you will also get a picture of what the league is like based on what they tell you or how good they may play.
Community
Community organizations are as varied as the community that it is in. Some examples of service type groups are Kiwanis, Lions, and Rotary International. Then there are traditionally fraternal organizations like the Masons or the Moose and Elk (who are now open to everybody). If you are a veteran, the American Legion and Veterans of Foreign Wars are a couple of the many options. As you can discern from this small list of examples the only thing limiting your involvement in a group is your imagination. Start by finding what is available in your area and the contact them to see what they can tell you to help you determine if it will be the right group for you.
The point is to go out there, make yourself available and have fun
Some of us have an easier time then others joining a group, but that should never stop you from becoming a part of something greater than yourself. Find someone who has extensive knowledge of your area like your local real estate agent and ask them for tips to get out there and join your local community. The first step may be your hardest, so stop thinking about it and get out there.