Some tidbits:

• Be prompt, generous, and sincere in your compliments. Ideally, don't use plain adjectives - use descriptions. (Exceptions here are compliments on articles of clothing - "your boots are AWESOME!" is kosher.) It only feels silly from your end. If you are just trying to make friends, avoid anything that (given your and the potential friend's genders) would appear laced with sexual interest, unless you can pull it off with genuine innocence and then reliably follow up with genuine innocence instead of changing tacks midway.

• Have a "standby" interaction prompt that you can pull out in lulls which isn't threatening, is generally well received, and provides a hook for further conversation. I usually offer people food. I'm sure there are others that would do - if you're trying to conduct an informal survey of something, for instance ("Hey, I'm trying to find out different ways people celebrate St. Patrick's Day, what do you do?), that would probably work too.

• Learn to pick apart people's dialogue for followup questions - you can practice this on fictional dialogue; just take a good-sized sentence and write down five followup tangents. Example:

"I went out to Cape Cod last week with my friend Tess and we found some sea glass."

Followups:

"Ooh, do you go to Cape Cod a lot?"

"Neat, what else did you do there?"

"Wow! How long did you stay on the cape?"

"Cool - what are you going to do with the sea glass?"

"Hm, I don't think I know Tess - tell me about her?"

Note that these all prompt the potential friend to talk, rather than providing an excuse for you to do so (any of the above would be preferable to, for instance, "Hey, I went to Cape Cod once and had the most fantastic lobster...") Also note that each sentence started with a particle that shows interest. Eliminating these runs a significant risk of making it sound like you're just interrogating the person. And: it is quite important that you actually want to know the answer to the question you pick. If you can come up with lists of five but don't give a crap about how any of them would be answered, you're talking to supernaturally boring people, you're a misanthrope, or you're doing the exercise wrong.

• Go ahead and be the first to suggest exchanging contact information. On the internet, this means e-mail or better, IM. In person this means a place to meet next, or possibly phone numbers or addresses (or e-mail or IM). It's scary to most everybody else, too, so don't expect them to do it. Leave a line of social retreat if they never want to hear from you again, avoid any requests for contact info customarily laced with sexual tension, but do make it clear that you think they're neat and you'd like to be their friend. You can even haul out the elementary school line "Wanna be friends?" - if it makes you feel more comfortable with it, go on a brief tangent about how "we lose so much when we leave elementary school and it's no longer socially acceptable to make friends by walking up to someone on the playground and asking if they want to be..." beat... "Wanna be my friend?".

• Cultivate social spontaneity. This one is hard to define, so I'll give an example. I was waiting for a bus and a woman I'd never met before in an awesome homemade knitted cloak tottering along on crutches said she loved my jacket. (It was my florally embroidered denim thing, by far the loudest thing I own). I was trying to make friends, so instead of thanking her and looking away, I fired back with a compliment on her cloak and soon had her talking up a storm about knitting. When she was interested in what I did with my spare time, I didn't talk about school, even though that was most salient to me at the time - I talked about cooking, gambling that the domestic handicrafts have some overlap in their aficionados. I told her I planned to make pumpkin bread as soon as I had a can of pumpkin. Which it just so happened to turn out that she had in her cupboard, and she lived in my apartment complex. So I went home with her, accepted the can of pumpkin, went home and made bread, and brought one of the loaves over to her place, where I hung out for another couple of hours chatting about textiles, her Hassidic Judaism, and her multiple personalities. (I am no longer friends with her over differences of opinion on a political/ethical matter, but it's still a great making-friends story.) Social spontaneity is what let me go to a stranger's place for canned pumpkin and bring her a loaf of bread later.