I've never cum, during sex or otherwise (or at least I don't think I have. Since the only info people can give me on cumming tends to be "you'll know when it happens" I have to assume that I haven't), so I can't really give tips on improvement. S&M however, (in small doses, ie: spanking and tieing up) is SOOOO much fun, as long as you're comfortable enough with the person you're doing it with. Take my advice (please) and settle on a safe word before hand. You don't want an "Oh God Stop" to slip out and stop your extasy by accident (trust me, it happens). Also, to start out with, use stuff that's not too scary, like stockings rather than rope, a guys tie rather than leather hand cuffs, a hairbrush rather than a spike studded paddle. You get the gist.