-Don't make a move too early
-Don't say the words "threesome"
-Don't make lead-footed suggestions about them "liking girls"
-Take drugs, preferably cocaine (and be the gatekeeper), if not coke then alcohol, mdma or magic mushrooms/lsd (if they are used to the latter two)
-Just be a fun person to be around until 30 minutes before bed time. Take "I'm tired, I need sleep, I don't feel well etc." as a bad sign
-Don't wait for explicit signs, unless they are absolute sloots they won't just say "Hey wanna bang", but listen to your intuition. Normal "I don't want to fuck" girl behaviour is not taking their bra off in front of you, taking lipstick off, laying next to you and looking into your eyes. You know this deep down and it's on you not to just be a fucking autist and dismiss because "well they didn't *say* they wanted to fuck"
- farting and putting lipstick ON in front of you is probably the best subtle indicator that they aren't going to fuck you. Abort if this is the case