Unlike most skills, making new friends gets more difficult as you get older. In grade school, finding a friend is as easy as locating someone on the playground of your approximate height and then sharing the last swing. As we age, we not only become more selective and self-conscious, but we are less likely to find ourselves in conditions which breed friendship. A New York Times article reiterates what sociologists have long considered the primary factors for forming friendship: "proximity; repeated, unplanned interactions; and a setting that encourages people to let their guard down and confide." By creating and encouraging some of these conditions, you can begin to make new friends.
Meet people -- and then meet them again. Follow your interests by joining groups, clubs, sports teams or religious organizations. You can also attend community events, volunteer or take a class (even an exercise class will do). Try to find something that meets once a week for a period of time, so you will see the same faces again and again. It can take time to establish rapport. If you're already a member of a group (work or school can count as a "group"), then be sure to participate in events and activities and stay open to talking and interacting with many different people.
Show that you'll make a good friend. After staring a conversation, be a good listener and show genuine interest in the person you are talking to -- make eye contact, nod, smile, make relevant statements and ask follow-up questions. Wanye Elise, a conversation consultant, suggests avoiding too many questions or it will feel like "an inquisition." He also says not to brag and that instilling some silliness into the conversation, especially if you are able to laugh at yourself, can help other people open up.
Encourage interaction outside the group. If you have something in common (you both can't wait to see a particular new movie, for example), say, "We should go see that!" and see how he or she responds. Or, you can be start smaller: "I'm thinking of getting a slice of pizza after the meeting, want to join me?" Sometimes, you have to be forward about planning future events. Friendships don't have "dating rules." It's okay if you're the one to suggests hanging out a few times in a row.