Honestly, I am still deciding on that count. Widowed about two years ago after 30 years in a straight, monogamous marriage and denying my feminine urges, and now single again and accepting my female side and bisexuality, I am still having a bit of a hard time wrapping my mind around what I want in a romantic partner (or even a one night stand), for either gender. All other things being equal, I still prefer female companionship. But I've had more kisses, cuddles and fooling around from men than from women since I became single again and started going out as a woman.
Here are my current thoughts. The first seven points apply to any gender. They would be equally true of a lesbian or bi girl or a TG person who was 'interested' in me.
First of all, they have to be nice to me. They have to treat me respectfully and sincerely seem interested in me and not just looking to get laid. No matter how nice they look, if they act or speak crudely and act like all they want is their own gratification, they are dismissed. I don't mind being touched affectionately while dancing or standing close to one another, but I won't stand for being groped and pawed like I was some back-alley working girl.
They have to be single, or in a definite open relationship where their partner is present, also talking to me, and clearly indicates that they accept adding me to whatever might happen between the three of us. I'd do a threesome, but I have absolutely no interest in a married person who is cheating on their spouse, or in someone who has a frequent boyfriend/girlfriend and is catting around behind their partner's back.
If they admit to smoking or doing drugs, even if it is just pot - which is legal in the state I live in - they won't get farther than dancing and chatting with me. My only social vice is alcohol, and I prefer that in my friends as well. Likewise, if they allow themselves to get excessively drunk, my interest drops to pretty much zero, no matter how well they score in other areas.
They don't have to be dressed to the nines, but a slovenly appearance will knock them out of the running.
Excessive tattoos or piercings (other than the ears) count against them. Large size gauges in the ears, larger than a dime, are a strong negative to me.
If they aren't Caucasian, they will have to score quite well in all other regards to get further than dancing with me. I'm not really looking for an interracial experience, but it also isn't a complete exclusion. That would have to be evaluated on a case by case basis, for me.
If they are nice to me, talk to me, and either offer to buy me a drink or ask to dance with me, then I may start evaluating them physically, as someone who I might want to do more with than just dance or talk.
Then, for the guys' physical appearance and other points:
I prefer a slender, boyish, almost feminine or androgynous look, slightly muscular but not overdone like a body builder. A heavy set guy might at least get some dances from me, if he is polite, talks to me and is attentive. I've even gotten pretty frisky with a heavy set guy once who scored well in all other regards. But someone who is seriously overweight doesn't do it for me, and a slender to average build is preferable.
He needs to be clean and well groomed, and to be taking care of his body.
He should be clean shaven, or have a well trimmed beard, and not have short, scratchy stubble or a bushy mess.
Preferably not excessive on the body hair though he need not be completely hairless in that regard. No hairy backs or chests so dense with fur that there is more hair showing than skin.
I don't really care how much hair is on his head, though I do find men with long, well-groomed hair somewhat more attractive.