I've watched mate centers sometimes and went in one for a roleplay mate once, because it was so hard to find anyone else for a roleplay mate. >_<
I guess you just make a character named "Mate Center", and go to Bonfire or Ficho.
Just gotta be advanced in grammar, and calm. Now scream "Mate center is open". :I Don't scream too loud, actually. lol.
Now there's peeps. Pick someone to go in the middle, and say to your fellow peeps "Who likes [PERSONINMIDDLE]?" and people should go near the derp. Males sit or stand and females lay or sit btw. ^^
So when people start to sit by the person, in a minute or so ask them "pick or pass?"
and if they say "I pick [CHARNAME]" then derp, job is done.
"Pass" is for well, passing for someone else.
That's just my knowledge about mate centers and how to run them. But be an expert: no caps spam and ultra neon! XD Also, do me a favor and don't be a tiny one, k? Lol.
It would be best to watch a mate center and see exactly what happens too, as Kikiory stated above.
Just to see what happens and see what they do, to learn for some experience I would guess.
Hope this helped. ^^