There have been many attempts to classify player types and what they seek to get from play sessions - for instance, this WotC marketing survey and this article on the RPGNET wiki on Creative Agenda.
How do you convince your players to sit down, take time, and discuss the player group and people's wants from the game as a social event, and what social tools/techniques do you use in this process?
A word of caution - this is good to do, but in moderation and taken with a grain of salt.
Before a campaign, I see what concepts seem to generate excitement and which don't, and ask people to send me privately cool things they'd like to see happen. Then as time goes on, debrief from time to time and see what people remembered that was cool.
But what people think they want and what they really want are two different things. I've had a lot of attempted debriefs, or discussions about what people want or don't like, completely spin out into the weeds. People will swear up and down they want immersive roleplay when in reality in the game they are 100% rules focused. I would concentrate on making the campaign awesome, and people will respond to that. In the end, trying to design art by committee is always doomed to failure.
All those "player types" and whatnot are fine, but I think they're best used as diagnosis tools by you and not as questions for them. If a player obviously responds to thing X when you do it, then that's the kind of player they are...
I ask our players to write recaps of the latest adventure, and to give a recap before we start the next session. I can tell a lot about what they found memorable by, well, what they remember! I can also tell what they found exciting or boring. In other words: forgetting something can be bad, but remembering it can be even worse, if they hated it!
Sometimes I talk to the players one on one, and I always try to pay attention to what they think about the game as it's in progress, but I think I get the most value out of their recaps. Also, on a related note, when they form theories about what's going on in the game world, it tells me a lot about what they think is interesting or important, and I can often use that as a cue to follow up on.
I don't have a mechanical answer for you as this is a lot like cooking. Dash of salt here, little paprika there. However here is the outline:
Notice I said pretty happy. Please some of the people some of the time, et cetera, et cetera..
Give everybody their 15 minutes, their time in the spotlight, give everybody a little bit of what they fancy ..
Ok enough with the cliches. So long as you take the time (via the methods outlined above) to learn what it is that the players came to the hobby for and take time to provide it to them, they will mostly enjoy your games and be happy to sit back when others are getting their 15 minutes.
It is usually better to give some of this stuff out individually as trying to fit the entire session to the moods and desires of several individuals is a pain. There will always be different 'wants' in a group of gamers from the guy who likes to act in their character to the girl who just wants to break people. The Guy will be happy to shut up and roll dice when the time comes if you've given him the chance to grandstand. The Girl will try her best not to turn every encounter into a combat fest if she is allowed to kill things from time to time.
To be seen to be doing this (even if it doesn't work out half as often as you like) will, for the most part, encourage the group to talk abouts its likes and dislikes as an extension of this group dynamic. You'll get feedback about how much combat the gun bunny is getting to participate in, and she'll start to compliment the actor rather than complaining about him getting in the way of her killing stuff.
Usually.