Okay this is a weird question for several reasons but basically #1 rule is that missing out on having sex with someone is not a big deal, if consent is not enthusiastic and obvious just err on the side of not getting it on. Unfortunately difficult to convince young people who haven't had much sex of the truth of this, but whatever. Rule #2 is be honest and don't lead people on. Of course this one will be broken because people are dicks but whatever it has to be said.