I haven’t done it myself, but I know someone who tried to organise some speed dating events, so I know a little of the proceedure.
They were held in a private room in a club, which had a bar, mood lighting and so on. The room was set up with 10 tables (say there were 20 people going)... you get a “free” drink (ie included in your ticket price) of champagne when you arrive, and one set of ten people are seated one at each table, the other set did the rotating.
You get 5 minutes (I think) with each person, and you were given a notebook to write stuff in to help you remember. I think there’s a comfort break halfway through the evening, and to get yourself more drink… Then at the end, everyone is allowed to mingle as long as they like, allowing you the opportunity to move beyond the initial 5 minutes-worth…
Afterwards, you let the organisers know on a form what you felt about each one. The choices being Interested, Not interested, or friends only. If two people match up on being interested in eachother, then the organisers will give out your number. If not, nothing further happens.
It’s meant to be fun, safe and harmless – a way of meeting a lot of people who you know are genuinely (one hopes) single and currently looking for something. I guess if no-one expressed any interest in you, it could be disheartening, but I seriously doubt you would have that issue.
Also, it’s probably a little nervewracking, but then everyone there is in the same boat, so you do actually already have a shared experience…
The only thing to be cautious of is that everyone there is a genuine participant, and not just mates of the organisers coming along to help with the numbers. But if it’s a company that have been organising them for a long time, (more than 6 months at least I would say) then that shouldn’t be the case.