How to close the deal with a girl I like?

Well the girl I like is shy but a very good person. I knew her from this year and at some points it seems like she is really intersted but to tell you the truth im not sure. I asked her to go to the movies and she was really cool about it. So we met and bought our tickets. We had an hour to waste so we played a few games. Everything was going great and fine untill we got into the movie. We decided watching cars 2 and it was a pretty good movie. During the movie I was watching for signs but I didnt find any. At one point I was pretty cold and asked her if she was cold, I was planning to put my arm around her but she looked at me pretty crazy. I was not sure if it was just me or not be she just thought I was a friend. When where on the phone and even texting she is all cool and looks like she likes me. Also dont forget that I said that she was pretty shy. Im planning to ask her out again but im not sure if I should make the movies or not. I really dont want to screw this up I like her alot.