Do they look like they want to rape, kill and eat me (not necessarily in that order)?
Whoops. Sorry. I’m a native New Yorker, and sometimes read things oddly.
Ayway, I’ll throw in the confusing datapoints from a old-fart bisexual, starting with general, then going into gender-specifics. And I’m assuming that the underlying question could be edited to “When approaching a member of the opposite – or desired – sex in whom you’re interested sexually (or potentially so), what’s the first thing you look at?” At least, that’s the question I’m answering.
First: posture. That gives some clues as to basic health state and mood. No point in approaching someone who’s tensed up and has hands clenched in fists, or is leaning towards someone else as if completely interested in that person.
Second: general affect. Do they look approachable? This starts with face: smiling? obsessed with something? aware of their surroundings?
Third: focus on face. Have they seen me? Have they reacted to me in any noticeable way?
Fourth: general body shape and details of carriage. I’ve a wide range of body types that appeal to me, so the question is more “Which area do they fall into, and how? Waify goth-boy? Rebenesque babe? Glasses-wearing geek?” (This would also affect my approach, should we get close enough to talk.)
Fifth: chest/breasts. I am not ashamed to say that I’m a white-meat fan, and the chest area and nipples will catch my eye, regardless of gender. And – and you may pit me for my closed-mindedness here – a man who wears – or should – a bigger cup size than I do is right out.
Sixth: Dress. Clean, neat. Doesn’t have to be the height of fashion, but it should be clean (as in that day’s sweat, and I shouldn’t be able to tell that you had eggs for breakfast by looking at your shirt), and demonstrating that they have an idea of what their body shape is and what looks good on it. This tells me that they’re aware of who they are.
Seventh – assuming I’ve actually been approaching them throughout this process: Scent. Fresh healthy sweat/natural body odor – YAY! Perfume that could choke a horse – BLEAGH! Stale alcohol and/or stale tobacco (especially stale cigar smoke): ERROR! RETREAT!
All of this, mind you, can be assessed in seconds, almost subconsciously, and change my decision from “I wonder what would happen” to “Friends only” during the approach.