>Never ever say "It was nice meeting you" and walk away

wait a second... I do that all the time. what's bad about it?

Was it really nice to meet them? Or are you trying to ditch them? When someone pulls the 'it was nice meeting you' gambit on you - are you relieved or do you like being ditched?

Oh man, life in Indiana is much simpler, it appears. We're good at polite nothings - nobody sane here would be offended at somebody saying, "Well, nice meeting you" and walking away. That's just how you say you're done with this particular interaction. If people don't like it, they probably move to Seattle or something.

  [..] do you like being ditched?

It's not about liking, but about understanding. I'm often not interested in talking to someone. Because I'm pretty regular, that means that other people often aren't interested in talking to me. That's just a fact of life.

  Was it really nice to meet them?

Autism alert. Such expressions are not meant to be taken literally. As a kid, I used to worry about not raking together the freshly mown grass well enough, because I was asked to rake together all the loose grass and the damned stuff kept slipping. That wasn't perfectionism, but something closer to autism: not understanding that 'raking together all the grass' was in no way meant to imply I had to even try to get all the grass. I used to get into arguments with my father about me being unhappy with my job of washing the car, because it wasn't actually completely clean. If you have such a problem, now would be a good time to start identifying these situations; it'll save you a lot of trouble.

It's ambiguous. That's the point. The relationship will remain ambiguous until it is tested in some way.

Some people -- not that I would stereotype us computer folks this way -- are extremely averse to social ambiguity, but most people are pretty comfortable with it. If they need to know something (does that chick like me?) they'll find out in the natural course of things (when they ask her out.) In the meantime, if they really, really care, they'll have some anxiety over it, but that doesn't apply to most interactions. You don't really need to know right now if that person found it nice to meet you, and rushing to figure it out only increases the chances that you'll end up believing something false.

Since people are generally okay with ambiguity, it's a no-brainer to them to observe identical social niceties in some situations regardless of their actual feelings. There's no point in alienating someone unnecessarily, especially since you might change your mind later. "Man, what a day. I hated the latte I got this morning, I hated the ham sandwich I got for lunch, I hated work, and then I ran into that wallflower douchebag at the grocery store. Come to think of it, it's probably just me; I hated everything today. wallflower is probably a decent guy. Maybe I'll invite him to my party this weekend." Because things can change moment-to-moment, even especially perceptive people who can see through the niceties treat a lot of what they perceive as provisional. They don't go back to their lair and add a row to their enemies database because somebody was a little frosty at the grocery store.

P.S. The average person's tolerance for social ambiguity is one reason why it's so frustrating to try to get tips from people who have a lot of social confidence. We go to great lengths to figure things out to increase our comfort level and avoid doing the wrong thing; they don't sweat it if something isn't obvious to them, and when they need to know something, they use a low-risk probe that at worst results in a mild but informative "mistake." Usually the real challenge is not an analytical challenge of figuring out the situation but a creative challenge of coming up with something to do or say that will turn out okay no matter what the situation actually is, and will hopefully yield more information so you can refine your approach.

Interesting.

you know what I don't like? I don't like not knowing if a person is genuinely interested or just being polite. I mean, the last thing I want to do is to trap someone into a boring (to them) conversation. I'd much rather they tell me they aren't interested. On the other hand, I don't want to avoid talking to people out of unfounded fear.

Really, the best solution is to have people leave when they are no longer interested in talking to me. (I mean, it'd be even better if I could get actual feedback so I'd know if they were bored or if they have other things to do but that sounds like too much to ask.) I mean, I try to leave people places in the conversation where they can leave if they aren't interested in my 'tales from the computer janitor' or whatever, but that's hard to do without sounding like I'm not interested in talking to them, so really it works out best when people are direct.

So yeah, speaking as someone without much by way of social skills, I depend on people leaving, or as you said "ditching" me when they are bored with me- I mean, sure there are subtle signals the socially skilled send so others can tell when someone else is bored. Sometimes I can pick up on those... but sometimes I can't. Like I said, I'm not very socially skilled.

You speak a minority language and will never persuade the majority to learn yours. On the other hand, it takes two to tango, and if they can't extricate themselves from an unwanted conversation with you, then either they aren't trying very hard (because they're passive-aggressive) or their social skills have limits just like yours. Either way, it's a combination of their weakness with yours that leads to awkwardness. By all means keep working on your skills, but try to see "normal" people as falling into a spectrum of social ability that you also fall into (deep in one end, apparently, but you'll be surprised how close some "normal" people come.)

I agree. I'm just trying to explain that this assumption that other people will break off the conversation if they are not interested is central to how I've overcome my own social anxiety.

That runs the risk of not extricating yourself. Maybe you go and meet those people over there and your new "friend" comes with you. Turns out those people are boring too, so you have to move on to the next group of people.

Saying "well, if you'll excuse me I'm going to get another drink/some food/whatever" is fine. They won't follow you unless you invite them (or at least they shouldn't), since that's code for "I'm ditching this conversation, bye!"

This strategy, as others have pointed out, is hedged heavily towards not ditching the solo "latch key" event attendee. For maximum effect, if you do try it (it's a rush), join a group that is seated by dragging chairs over (demonstrates maximum commitment) to sit down with the new group. A lot of what the other posters have said - it's nice meeting you is average social lubricant. What this strategy espouses is focusing on the other person, not you. You presumably are indifferent to 'nice meeting you' rejection. This is about not making the other party feel rejected. As a bonus, it makes you into a leader - organizing disparate groups, bridging cliched cliches...

This is the best advice. You don't have to leave a person, you can recruit them. It also works with people with whom you don't get along at first.