There are many different hints on if guy likes you or not. Some guys can make fun of you, that's just how some boys show that they like you. Others will help you around at school, etc. They will also flirt with you and always be by your side.
one of my friends swears this is the way... if you're sharing a plate of food and he gives you the last bite. I knew when I got fired (the one and only time) from a job, I came home crying, he says "whose ass do I need to kick? " when I told him I was fired "is that all? now we can go on vacation"
By his actions, his concern and treatment of you. "I love you" doesn't mean anything if that person treats you poorly. If this is a new relationship, then he will be completely focused on you, your wants and your needs. He will want to spend all of his free time with you and he won't be able to keep his hands off you (I don't mean in a sexual manner).