What are the basic rules of swinging?
The short list that holds almost everywhere: consent is asked for and can be withdrawn at any moment; a no needs no explanation and ends the approach; each couple agrees its own limits and a veto before anything happens; nobody is owed anything for showing up; what happens stays private; and safer-sex terms are settled in advance rather than in the room.
There is no universal rulebook. Every couple writes its own version, and clubs and events add house rules on top of it. But a small number of rules hold almost everywhere in the community, and they are the ones worth knowing before a first event. This answer is that short list. The club etiquette answer covers how to behave inside a venue, and the answer on setting rules as a couple covers how the two of you write your own.
Consent is the first rule and the one every other rule depends on. It is asked for at each step rather than assumed from the last one, it can be withdrawn at any point, and a no is final without needing a reason. A couple's decision to attend is not consent from either individual to anything in particular; each person answers for themselves. Enthusiastic agreement is the standard, and politeness is not agreement.
The second family of rules concerns what the couple agreed before they arrived: what is on the table, what is off it, who does what, and how either partner can pause the evening. Agree it sober and in advance, write it down, and accept that the agreement can be revisited afterwards but not during. A veto that is honoured instantly is what makes trying something new safe; one that gets argued about is what turns a good night into a bad memory.
The third family is behaviour in the room, which mostly comes down to not imposing yourself: ask before approaching, take a no gracefully, keep your hands to yourself until invited, put phones away, and do not press anyone to drink, to stay, or to move faster than they want. The fourth is privacy: no photographs of anyone without their explicit consent, no identifying details shared, and no stories that would let someone be recognised. Discretion is not a courtesy here so much as the thing that lets people attend at all.
The fifth is health, and it works best as a conversation rather than an interrogation: agree safer-sex terms before anything happens, ask about testing and protection without treating an answer as a verdict on a person, and say something if the terms change. If a rule is broken or someone feels pressured, leaving is always allowed — that is the rule underneath all the others. The answers on club etiquette, on consent in the lifestyle and on STI testing in the lifestyle go deeper on each of these.