Meeting through friends was the number one way singles meet people. According to Assimos, the bar is the one place where most of the people there are guaranteed to be looking to socialize, even if their first intention is not to meet someone.
For instance, if you want someone who's a fan of a particular sports team, go to a game. What are their hobbies? If so, what do they like to do? Once you have an idea of what your ideal partner is like, find places and events where they're likely to be. According to Lipman, turning to people closest to you is a great idea.