To understand a person and especially girls you need to talk to them. Make sure she faces you when you are talking and have self confidence. Always be yourself when talking to them and if she shows disinterest in you, don't show interest to her. If she talks to you looking somewhere else, know that she is not interested. When she looks at you for long, she wants you to talk to her. Girls are happy when you ask for their number.
Believe me, sometimes it is as difficult to understand some guys) :) But I'll try to answer)) We change our mind a lot. There are always many-many factors that affect our decision-making. Guys think we do it in order to freak them out, but it's not true) And yeah. You will never understand how it is possible to have a closet full of clothes, but still there's nothing to wear)))) :D
jaja good question, im a girl and i dont even know!(; maybe cause we are built differently from you boys. but i know that sometimes we do that on purpose....not always though! its just another thing us crazy women do!;p hope i helped!!