I've only done it once but it was a laugh.
You'll get about 3 mins with each person which can either feel like the shortest or longest 3 mins of your life. You need to think of interesting questions to ask if you want to stand out (why you want to stand out will become clear shortly) as everyone generally asks where you come from and what you do for a living. That gets pretty boring after about the 5th person. You then make a note of whether you liked that person- you should do this right away as you will probably forget.
At the end of the time when you have been round everybody so to speak, everyone fills in their forms marking the people they want to contact again – this is why you want to stand out. If you have ticked someone and they have also ticked you, the organisers put you in touch with each other. Obviously to maximise your chances you could tick everyone but I'm not sure if the organisers are wise to that.
Go with an open mind and ready for a laugh and you will enjoy it. I would suggest that you go with a friend as there is a bit of hanging about at the beginning and it's all a bit awkward.