I'm noticing that the older we get the more difficult it becomes to make new friendships. When we're little, a simple "hello, I like your shirt" is enough to forge a bond that lasts until one of you steals the other's crush. At any rate, when we get into our mid to late twenties, your peers get harder to approach and if you do manage to strike a conversation it doesn't go beyond acquaintance territory. People seem to be really resistant to expanding their circles; the so-called ice is harder to break than ever. Friends of friends have provided with a slightly better friend/acquaintance ratio. But even so, friends go abroad, move out, and hell, they're even starting to get married/have kids. Leaving us with a smaller pool of friends (not to say marriage ends friendships, but it definitely changes them). I am writing this as a form of mutual brainstorm; I want to come up with the most effective ways to make friends as an adult. Here are some of my ideas:

• Get a job. There are real live humans working there, however, depending on the job, you may have very little in common with them. We all need money, so you probably need a job.
• College. As you further your education you'll meet people that have very similar interests whom will spend a lot of time with you provided you are approachable and studious. You'll see some of them quarter after quarter even. Only bad side of this is if you start dating/break up things could get awkward since you can't really avoid them. If you go here, it's hard not to make friends.
• Join random internet meetups. Danger and awkwardness level is high, but it's not too bad specially if you're just moving in to a new area. Do sparingly.
• Co-ed sports team/league. You get to exercise (a little) and from my experience this is basically and excuse to drink and meet some active and outgoing people. High chance of meeting cute girls/guys. Takes some guts to join by yourself.
• Old friends. Say hi to that buddy of yours who you haven't seen in months, take your friend out of a coffee or some beers. This is almost like dating, with a courtship of sorts, you have to show your best self. There's no romance though, or there could be? You do risk finding out that this friend actively wanted out of the friendship, but eh, the reward is worth it.

Do you have any other ideas of how to make friends as an old and withering young adult?