Usually look for posture - is the demeanor relaxed, happy? Typically a good sign. Smaller groups, while more tight knit, can sometimes be easier to make friends with and become a part of their dynamic. That’s what happened to me. Groups that are too big often fracture. It’s very true that quality > quantity is best. Or start with someone sitting alone reading a book/watching something. Maybe you noticed what book/movie/game they were playing and you like it too. Good conversation starter.