How do you to talk to a guy, who u dont have any classes with nor do you know him. Just a guy you see in the hallway all the time, and like.

If you ever see them just hanging around during a break or passing period just stop and say hello, engage in a conversation with them. Maybe try and find them on social media after you learn their name to further the conversation.

You walk up to him and be like hi i know this seems weird me walking u to you and i don't really know you and i know you don't know me but would you like to become friends or talk sometime just to get to know each other i see you in the hall everyday and was just wondering?