It should be a series of check ins as you progress with a person. An example is “is this okay?”. I also tell my partner to let me know if they want me to stop for any reason and that if they want to stop it is okay and I want them to be safe happy and healthy. Now that I’m in a serious relationship,I tell my partner that too, because just because we have had sex before doesn’t mean I can assume sex every time . And I never have we with my partner if they are too drunk, even if they want it, because if they can’t remember it in the morning it is not acceptable.