Check out my post, 'Girls: how to tell if a boy likes you' also check out my latest one, thank you. -Rhian
The biggest sign to me that a guy likes a girl is the effort he puts in to developing the friendship or the relationship. A guy who doesn't talk to the girl for days or puts virtually no effort on progressing their relationship most likely doesn't like you that way. However, it's not always like this. Just a little general rule of mine.