Texting during the party
They’ll laugh out loud standing alone, reading a text, they’ll smile or smirk, exchanging a private joke on whatsapp.
Hanging out at the bar, rather than socializing
They don’t have an inviting smile just an inquisitive expression directed at no-one in particular.
They are surrounded by same gender people
They look for places to sit rather than stay on their feet
They leave the party early