This is a great question and point about the sexual taboo that women unfairly deal with. I think its unfair to label women who want to have sex but not really a long term relationship. Its 2019. Sex is natural to a lot of people. Its an unfair taboo. The men who can allow a women to be up front without fear of being judged, is turning himself into fun fk boy. Thats pretty much it.
That's why honesty is the key, literally. State your intent, and if she's down, she will let you know. The best thing to do if you want 'get in her pants' is to just make it known that you are trustworthy, and nonjudgemental. You are ok with her desires and she can be herself around you without fear of being judged. Of course thats not my game, but the sex game is a game a lot of people play. For me its about having no boundaries in meeting women, and pretty much going for the qualities I look for above all else.