Draft up a checklist (physically or mentally) of what qualities you want in a sexual partner. Whether they're an anonymous fling, a casual affair or a long-term relationship, it's important to be conscious of what you will and won't unzip for.
Age, intelligence
level and marital status are a good place to start, but also factor in sexual
attraction, apparent cleanliness and, on a big night out, a guestimate of their
blood-alcohol level. Your criteria should be partner-specific, but also
condition-specific. If the partner is ‘perfect’ but the conditions are dubious
(you’re in a rush, others are in earshot, or the location is dodgy), give it a
miss. You’ll be distracted and uncomfortable throughout the whole experience,
very unlikely to experience significant arousal, and even less likely to cum.
Also think about what the purpose of the sex is - is it for fun? power? revenge? to try something new? What are THEIR reasons for wanting to have sex? This will determine what kind of partner you should go with.
Lastly, TRUST YOUR INSTINCTS. If someone seems dodgy, coercive or aggressive, avoid them like the plague (unless you're into that). Similarly, if they're needy, anxious and insecure, probably better to skip the sex. You could end up with a big mess on your hands.
Make sure you stick to your criteria - it's an important benchmark to make sure you have some power over who you fuck, when & how. Sex is wonderful - you deserve to have the kinds of sex you want.
What are YOUR criteria?