How do you let a guy know that you genuinely like him through nonverbal signs?

Being a guy myself, the best clue I have to when a girl likes me, is if she makes random complements. For example, there was a girl that I met, and within five minutes of my meeting her she said "Wow...You have really pretty eyes!" less then a month later we were in a relationship. I'm not saying that you should tell him he has pretty eyes, but find something you really like in him, and let him know it.