Im 19 and im kind of clueless about women and the way they act.

Im currently in college and want to approach them but I mostly see them busy either on their phones, reading, or studying alone or with friends which makes me think twice before saying a word

How do you guys read the body language of a woman? What do I need to look out for? How can I have more of an open body language? Appear more friendly? Because I have a serious face and I feel as if that plays a factor also.