Places to meet entirely new people: work, school, clubs (by that I mean like, places where hobbies are done: tramping clubs, etc.), online.

Places to meet people who are friends of friends (and therefore likey to become your friends): parties held by existing friends, clubs of friends.

The hardest way to meet new people I at bars and clubs. Of course you can do it and I have, but chances are you have less in common than a friend of a friend, or someone at your workplace, school, club. See how it works?