I don’t advocate waiting around forever before you show your interest - far from it; I believe in really listening and paying attention to what a woman is telling you (and it may be by glance, smile, body language) - and then, revealing your own interest as she reveals hers.
This process may take a while; on the other hand, it may take only one night - in the right circumstances.
For example, say you meet a woman at a party. You start to talk to her, in a scrum of other people. Does she appear really interested, or is she glancing around, looking for some friend of hers?
If she is interested, offer to move to a more quiet part of the room. Will she go with you?
If she does, say to a sofa, is she sitting tilted towards you? Is she smiling at you? Do you feel you have a real “connection”?
Now you have been talking a lot with her that night. You may move around, but somehow you always find yourself talking with this one woman. She seems to welcome this, or even makes it easy for you - reserves your seat on the sofa to when you go to get a drink, that sort of thing. You now have a choice.
If you want to play it safe and take it slow, you say something like “it’s getting late, I gotta go, but I must admit I have had a really fun time with you tonight. Do you want to keep in touch?” If she says “yes”, and gives you her number, you call her soon and make plans to go out for coffee or drinks, or to go do something fun; and at this later meeting, you indicate your interest - if it seems appropriate.
Alternatively, if you are feeling bold, you say something like “It’s getting late, this party is breaking up - do you wanna continue this at my place?”. If she goes back to your place, chances are she is interested in the same things you are.
Worst she can do in either case is say “no” (and if she does, don’t press!). Chances are, if she has been having as good a time as you think, that she won’t. Why should she? She’s had a good time with you so far. If she wasn’t interested in you, she would have let you know, by indicating that she would rather talk to someone else, or by body language.
And if she does say “no”, so what? There are a million reasons someone doesn’t want to get physical with you - maybe she really likes you, but she is comming off a bad relationship. Whatever the case, you can be sure it isn’t because she wishes to humiliate you or something bad like that - just play it casual, no hard feelings, and try again with someone else.
Use this approach and you are guarenteed to not lack for female companionship.