I always got to know a guy before doing him. I've known guys I only had sex with once, but it wasn't a "one night stand" as we were friends before and after. Sometimes hormones get going and you just stumble into sex with someone you already know. But, I've never picked a guy up and had sex with him. The thought of doing that always scared me, and I don't scare easily.
I've had plenty, sad to say. Back in my rebellious teenage years, you know sneaking out, drinking, one night stands, etc. the usual. thankfully i've seen the light and if i would have known then what i know now, wouldn't have done them.