At our club we prescreen all members by means of a questionnaire. When we come across a single guy we think may be a good fit for our parties, we meet them in person to make sure they have the social skills necessary for a sex party - before they are extended an invitation.
Although there have been one or two guys that passed the screening process, and then come to a party and stare or otherwise bring an element of discomfort, 99% of the time we catch the unsuitable ones when we meet them or from their questionnaire. For those who slip through, they are not invited back. If a problem is caused during the party (Not happened yet), then they are asked to leave.
We have a lot of single women and married women in our party group who feel very comfortable with this process and come to parties. Some want to get down and dirty with a lot of guys, some just one or two - but either way they get pre-vetted guys to play with and its a great experience all around.
We have been to parties where there is such an overwhelming proportion of single men, that women have not played, simply because in such an atmosphere, the men tend to be highly charged and will join a scene without asking or breach other etiquette. This does not contribute to a good vibe for a sex party
We have found the ratio that works for us is 1.3:1 men:women. Any lower and the women start asking where the guys are, any more and you start getting issues.
So basically, what works for us are: good quality guys (personality & physique), and optimum numbers.
