1) Listen for clues: If you listen carefully enough, he will drop clues in your conversions with him.  When he talks about his day and he mentions that he was thinking of you or of you two as a couple, then you know you are on his mind all the time. This is a sign that he is interested in you!

2) What do his friends say and how do they act around you: If you know some of his friends, they can also provide insight as to whether or not this guy likes you a lot.  If he talks about you all the time with them, it will come out when you are around.  They might joke around with him about how much he talks about you.  You can also tell by the way his friends treat you how much he likes you.  They will treat you with respect and put you on a pedestal if that is the way he is talking about you.  If his friends are not sure who you are, then you know he's not interested.

3) Body Language: Even if you have not been dating this guy very long, he will be anxious to touch you if he is interested.  Even if he is just making an effort to stand close to you, you will know he is attracted to you.  If he doesn't make an effort to be near you or if you have to be the one to make the first move, you might want to rethink pursuing this one.

4) Communication: If your guy is texting you constantly or calling you all the time just to see how you are doing, then it's a no brainer, he's into you!  If you have to be the one to initiate all communication, then stop wasting your time.  And as far as in person communication goes, make sure he is open with his feelings and tells you what is on his mind.  A guy that is interested in you will be willing to open up to you and show his more vulnerable side.

5) Intuition: You always know deep down when somebody likes you a lot.  Don't fool yourself into thinking he is interested just because you are infatuated.