This does not mean that the girl will serve them all. But the more signals you notice and the more often this happens, the higher the likelihood that your signs of attention will be accepted with pleasure.
So, a girl likes you if she:

Smiling at you.
Gives you short glances.
She looks away when you look at her.
Long looks into the eyes.
He runs his fingers through his hair.
Licks lips.
Shows off the neck.
Tilts his head towards you.
Turns to you, sitting on a chair.
Touches your arm or shoulder.
Laughs when you speak.
Strokes an object in his hands.
If you notice some kind of signal, this does not mean that the girl is ready to marry you. She just finds you attractive and doesn't mind if you make the first move. It can be a conversation, an invitation to dance or a cup of coffee.