There's a cute boy that stares at me not constantly but when he does we just smile at each other what does that means?
When a boy is staring at you?
Boys sometimes have weird ways of showing interest in girls, and staring is just one of them. The boy simply likes you a lot, and it appears you like him as well since you describe him as cute and you smile at him too.
But there one more point, he may be looking at her to find out weather she's good looking ? To look every thing in her face...