I can't contribute any experiences, but I thought you might find this article of interest: Six thinking points before playing with someone new. Though it refers more to going home with someone one has met at a club or wherever.
Yes, the good thing in a club environment is that you can have fun with knowledgeable people around who see what's going on.
An event sponsored by a trustworthy organisation or society does not, unfortunately, mean that everyone who shows up there is trustworthy.
So as TG says, asking for references seems a smart thing to do. You don't need to say 'Wait, I want to ask around first', you could just ask 'Anyone here you have played with?' If your potential play partner can't refer you to anyone who can attest to his/her abilities, it should be easy to say 'In that case, no thanks.' If your suitor can point out people he/she has topped, or who have watched him/her topping, you have already made some more acquaintances.
Instinct is still important, obviously. Shifty individuals vouching for each other don't count either...