#3. Be Up for Anything
Once you're out with your new not-quite-friends, discovering new shared interests and not-coincidentally drinking heavily, you'll want to keep the good times going. Every minute you spend with these people is precious, time to turn them into friends, or failing that, time to meet one of their friends. Also, as time passes and they're still around, that's an excellent sign that these people tolerate you.
Toleration: The bedrock of any friendship.
So be open, available, and eager. When someone suggests another round, buy it. When someone suggests getting pizza, cram that pizza in you as fast as humanly possible. When someone suggests going to another bar, fucking carry them there.
Me: -blinking- Hey, where did everyone else go?
Shifty Co-worker: They had to bail awhile ago.
Me: Man I'm drunk. How did I not notice that?
Shifty Co-worker: You've been having a lot of fun.
Me: I have, haven't I? This has been a wild night! I'm glad I came out with you tonight ... why are you wearing a diaper?
Shifty Co-worker: -wearing a diaper- This is a diaper club. How drunk are you?
Me: -sees everyone in club wearing diapers- Feeling less drunk quite rapidly now. Wait. -just now seeing the diaper I am myself wearing- I think I gotta go.
Shifty Co-worker: Yeah, you've made that joke several times now.
Me: That does sound like something I'd ... poo.
Shifty Co-worker: That one, too.
Me: How on Earth did you talk me into coming here?
Shifty Co-worker: You said you wanted to meet people.
Crazy Diaper Fetishist: Hey, how ya doin'?
Me: -remembering it's important to be up for anything- I did. And I guess this is better than sitting around reading things on the Internet.
Crazy Diaper Fetishist: Less weirdos here, for one.
#2. Join a Social Group
Another good way to meet new people is to thrust yourself into a group of people who already have shared interests with you. Volunteering, playing recreational sports, joining a professional association, that kind of thing. Because you already have something in common, that initial conversation is always easy.
Also, many recreational sports teams are really just poorly disguised competitive drinking teams.
Me: OK, I think I get it. So you guys are just into the diapers. You don't all act like babies.
Shifty Co-worker: Adult babies and us have a lot of overlap. There are a few of those in a room in the back.
Me: Oh yeah. I found them. -eyes widen- I somehow suspect everyone's having a better time in there than all the crying would suggest.
Crazy Diaper Fetishist: Personally, I think those guys are freaks.
Me: Riiiiiiight. You just like shitting yourself.
Crazy Diaper Fetishist: I prefer the term "messer."
Me: I'm sure you do. But just to be clear, you are actively pooping yourself right now, while you're making eye contact with me, aren't you?
Crazy Diaper Fetishist: -licks his lips too-
Me: Well, at least I'm making friends.
Shifty Co-worker: Oh, we're not your friends.
Me: You're not?
Shifty Co-worker: No, this is just a sex thing.
Crazy Diaper Fetishist: So which one of you guys is changing me and which of you guys is going to beat me off?
Me: -starts running, never stops-
Finally, for the terminally lonely among you, you might be surprised to learn that traveling is often one of the easiest ways to meet new people. It turns out that when you're traveling, the people you find yourself hanging out with will be, as often as not, other travelers, just as eager to meet new people as you are. Also, because you're always on the move, you'll have the ability to walk away from any disastrous encounter. If you make an ass of yourself, that's OK, because you need never see this person again.
"So those aren't actually mirror pants? Right, that's me off then."
And of course, traveling is also useful when creating a new identity for yourself, far away from everyone who knows the things you've done.
Me: So what'd you get up to this weekend?
Backpacker: Was up in the Lake District.
Me: That's cool. I love lakes. Well. Just a normal, healthy level of interest in lakes.
Backpacker: Nice one. So what made you decide to go traveling?
Me: Ahh, you know. I had an opportunity to ... abruptly leave home without telling anyone, and kind of jumped on it.
Backpacker: What's that crinkling sound?
Me: That's me. I got excited thinking about the lakes.
Backpacker: Are you wearing a diaper?
Me: Turns out I couldn't run from everything.
Backpacker: -long open-mouthed stare-
Me: It's totally normal, though. We can still have shared interests, about diaper or non-diaper activities. I don't even need you to beat me off.
Backpacker: -long open-mouthed stare-
Me: You weren't about to offer to beat me off, were you? Before I shot that down?
Backpacker: -long open-mouthed stare- Where were you from again?