I look for consistent eye contact, every now and then some form of maintained contact (like his leg pressed against mine, or his arm consistently brushing against mine), most likely leans towards me instead of away and if I say I'm with friends he makes an effort to say hello to them.
I'm not always sure if he's interested, cause some guys can just be really nice and polite because that's their personality not cause they're interested. But if I stick to the signs I've mentioned above, 9/10 I'm right
I personnaly doubt a lot, and have hard believing a guy is serious about me, even if he flirts a lot. I guess I just wait and watch him from afar, if he gets tired of flirting with me, how he acts around girls, how his friends treat me, how kind he can be with me.
A real hint for me is when I can say "he doesn't treat me like other girls", or when his friends seem to try to make him jealous.
But I never feel confident, not until he asks me out for real.
We're not all like that though, I guess a lot of girls are more confident than me, and take hints faster too.
What Guys Said 2
Yepp, they are unsure as can be seen on this very site. Like the other anon guy said, they constantly second guess themselves ...kinda like some guys often do too
They are always unsure because they are Ninjas when it comes to self-sabotage and self-doubt. They can second guess themselves into uncertainty in a way that would make a man blow his brains out.