Sexual consent is about having the ability and freedom to agree to sexual activity. This is something that must be clearly established between two people before any kind of sexual act or behavior, and you can change your mind at any time.
Unfortunately, your judgment can be dramatically impaired while you’re under influence of drugs. Before letting anyone come to your place (if you’re hosting) or before coming to a session hosted by other people, establish a set of boundaries, particularly about what you and other people are and aren’t prepared to do sexually.
Remember: sex without consent is rape, and rape and sexual assault is a crime.
If you don’t know how to tell the other person, you could show this song as a message of you not willing to have sexual intercourse.
If you’re hosting, it’s your responsibility to ensure that no one in your session is being forced to do something that he does not want to.