Hm. Here are some things I look at;
1. Reciprocity. I do things for my friends. Do they return the favor when I need it? Are they reliable? I had one friend who I drove to her job each morning, drove to school at nights and picked her up at time when I didn't have much time. She had certain responsibilities; helping with my kids and paying rent. She didn't follow through with rent and didn't help much around the house (though she was willing to make craft items for extra money to try and get a guy she liked to be able to visit a convention she was helping with.) So that downgrades her and I won't invest in her as a friend beyond the minimum unless she really makes up the slack. There's no reason to alienate her, I just don't want to give TOO much more than I get.
2. Invitations? Do they invite me to things? Do they show up when I invite them to things I'm doing?
3. Are they supportive? Will they defend me to other people? There tends to be a 'halo' effect where if you view someone positively in one way you view them positively in others.
4. Can we communicate and solve problems? What kinds of topics are off limits? Will they be honest with me? I prefer friends who are positive but who can also voice their honest opinions. (Ask, vs Guess culture.) I strongly prefer askers, but I try to meet people where they're at.
https://www.theguardian.com/lifeandstyle...er-guesser
Also, do they tell me about personal things in their life? If not, they're more like an acquaintance. There's nothing wrong with that. I just don't want to over-commit.
5. Are they interesting? Do I respect them?
6. What are their boundaries? Everyone has anxieties, idiosyncrasies, etc. Can I accommodate them? Can I meet them where they're at without too much trouble? What kinds of demands will they make on my behavior and speech? What sexual or political ideas can I express around them without alienating them? Ideally, good friends will tolerate some ideas they don't agree with. General comfort is a big thing. Someone who hugs their friend goodbye but not me is an acquaintance, not a friend. Being able to read body language and identify nervous gestures is important. If someone is anxious around me, I give them a lot of space unless they start acting differently.
I don't know if any of that helps you, but good luck.
If it makes any difference, probably 75% of my close friends are female.