I'm married now so this doesn't apply to me at this time, but in the past if it was going to be casual sex and nothing more the guy would have to be very good looking, very good in bed, respectful, but with basically nothing (else
) in common with me so it was clear there was no future. So basically make an effort to be really good in bed, but outside of the bedroom be boring.
Choose someone you have little in common with outside of physical attraction.