thanks mischief and all the other ladies who have added their support.
As an ex-single-guy (well, I'm still a single guy, but I'm not a wannabe-swinger-single-guy anymore), one thing I think often gets forgotten in the various hints and tips that get passed around is that, all women are individuals. There's not one set of rules that work for everyone; you have to read the woman's advert and/or her posts in the forum and try to make a judgement on the best way to approach her.
As an illustration; when I first started doing this stuff, I used to write long romantic missives that were one half sexual fantasy, one half autobiography, and one half expressions of sexual attraction. After about a dozen I started to get a bit frustrated about the lack of response, and I read in someone's advert that people were writing too much for her to read. So I started writing less, making it more chatty, trying to draw people into conversation. A month or so later, I read in some advice document that women get really pissed off at long email conversations that don't lead to meets, so I changed again, usually ending messages with an invitation to exchange a few emails "with a few to meeting if we get on". I was always including a facial picture and sometimes a body-picture, but a few months later I found in the advice section on AdultFriendFinder the advice to always include a gential picture "so women can see what they're getting". Then I read somewhere about women not liking being pressured into meeting. So I changed again. And again. And someone else said that women hate getting genital pictures in their mail. And women hate getting any pictures attached to replies. And women hate getting replies without pictures. And women need to be wooed with long romantic fantasies. And you should should never say anything in a first message that doesn't directly compliment a woman. Never talk about the weather. Never leave any room for misunderstanding. A little vagueness goes a long way. Be honest. Be a fantasy. Sell yourself. Never tell women you've got an advert of your own. Never PM a woman in the forum. Only PM a woman if you've established a rapport already. Feel free to PM women to be chatty. Do this, do that, blah blah blah blah blah blah blah.
Finally, after a lot of mature reflection and shooting steam out of my ears, I realised that it's all bollocks. People are individuals, and that includes women on swinging websites. Different people like to be approached in different ways, like to be treated in different ways. There's a few nearly-universal rules that can reduce the chance of you looking like a completely thoughtless moron, but otherwise... everyone's an individual, and that includes the single guys. Just be yourselves.
Unless your real self is a monosyllabic selfish bastard, I suppose.