It's been an interesting experience, watching friends chase their different dreams - from those who just want hit-and-run connections (or, as foobiwan put it 'single-serving girlfriends') to others who crave that all-consuming, meaningful exchange that can stir the soul.
If there is a unifying theme in the romantic lives of friends in this past year, it would be the stunning lack of prudence demonstrated by its protagonists; I spent the better part of 2002 watching a tapestry threaded with fool's errands and self-absorbed betrayals woven before my eyes.
maradydd's outstanding essay Emotional Investment Banking, Fear of Commitment and the Quest for Ass is well worth reading; unlike many otherwise intelligent women I know who jump from relationship to relationship (all the while vacillating between  gushing about how perfect and happy happy happy they are, and  neurotically despairing over some insurmountable emotional obstacle) maradydd demonstrates a certain lucidity about relationships that sounds quite alien coming from the distaff side of my circle of friends.
Emotional Investment Banking, Fear of Commitment and the Quest for Ass
Ahhh ... expectations.
Every new relationship has 'em. They start out as dreams, as hopes, as desires -- no relationship ever starts without desires. At first you hope that the person you're interested in will be interested in you, too. That gets borne out. Then you hope that there's some substance to the desire, that the interest won't stagnate, that they'll continue to be as exciting and unique and fun as they were at the very beginning of the relationship. Gradually, if it's going to go long-term, these desires get substantiated. They become expectations.
Or, if you're not careful, they become expectations early on in the process, long before they deserve to be, and you end up disappointed. I can't begin to count how many times I've heard half of a bitter breakup say, "He/she just wasn't the person I thought he/she was."
Unfounded expectations are the #1 killer of relationships today. Speculating in a relationship is like buying stock on margin: when you overextend your resources, there's a slim chance you'll make it big, but it's far more likely that you're going to lose your (figurative) shirt when your partner's ass can't cover the checks that your own heart wrote.
There are two tactics, I think, for avoiding the bust that comes from overextending your emotional resources. I'll call them the Careful Investor and the Day Trader.
The Careful Investor evaluates his prospects thoroughly before putting in any emotional capital. Potential relationship material might not even know he's considering them, because he plays his cards close to his chest. He delineates friendships clearly; you always know where you stand on the surface with a Careful Investor, because his words and his body language tell you. He forms a picture of his interest in his mind; maybe he even has a picture of his Ideal Interest, compares the two, and seeks out the one who matches his ideal the best. If he knows what he's doing, he refines this mental image of her down to a very high resolution before he makes his move; maybe in the past, he didn't look closely enough and missed a major incompatibility. He moves only when he feels ready, and most of those moves are calculated to maximize his return on the investment of his time and emotional capital. He's careful with his body language. He's witty and clever. He figures out what his target will find most appealing and approaches her from that angle. And if he's done his homework right, if he knows what he wants, can find that embodied, and isn't fooling himself about who the girl really is, he will get it, and he'll throw body, mind, heart and soul into it. She'll get all of him.
If, that is, he ever approaches anyone at all.
The Day Trader keeps his eyes out for what looks good at the moment. When he sees a likely candidate -- using whatever criteria capture his attention ("Wow, look at those tits!" / "Goddamn, she's smart!" / "Hey, she likes bicycling too!" / etc.) -- he starts to spend his readiest and cheapest resource: time. He flirts. He takes her out to the movies, goes out for coffee with her, whatever will net him two things: details about her and fun. He asks lots of questions. He invites stories and tells some of his own. He finds out what she lives for, what she dreams of, what really winds her clock. He does nice things in good faith, putting himself out perhaps farther than he has to, but not so far that he's going to end up in debt or seriously disappointed if Things Don't Work Out. Maybe he gets laid. At this stage, he's all about a mutually assured good time.