If u want ur crush to know that u like him you have to flirt a little bit. U want him to know that u notice him. If u flirt with eveyone he's not going to no u like him and he's going to think ur just being a flirt. So if ur next to him maybe bump into him and say ops sry or push him gently. Trust me if he didn't notice u before he will defintley notice u now.