Getting to know someone is the key to being sure what you are reading in their body language, is true
However, there are some signals that are generally the same for all guys. listening to you and laughing at your jokes, is a sign that this guy really wants to get along with you. if they look nervous, probably means they like you. if they give you a stare with a raised eyebrow they could either be prepared to compliment you, or admit their annoyance by your presence ...etc...