The other day, I indirect opened a girl while waiting in line at a drugstore. I asked her about her scarf, and we started talking. While we were talking, I noticed that she had her arms crossed and her body was sideways to mine (I was standing with my feet pointing at her and her body was perpendicular to mine). Normally these are not good signs.

However, she was playing with her hair almost manically (touching, playing, and brushing it every 3 to 4 seconds it seemed). She also had her face turned towards me and her eyes were attentive and she seemed very interested in the conversation.

Anyway, I let her go to the cashier to pay, and when she is about to finish, I go up to her and ask for her number. She sticks around as I buy my stuff and then puts a number into my phone. She also asks for my name and we go are separate ways as we leave the store.

Anyway, good sign. I was wondering, though. Do you normally get mixed signals. This was an extreme case, but I was wondering whether negative body language like that just indicates nervousness at being approached by a guy and not necessarily lack of interest.

The signals are hard to read. Arms crossed, for example, can mean either that the person is guarded, and doesn't want to be approached, or that they feel closed off within themselves, and can't break out of their own hesitation.

Sounds like you went for it properly and saw good results. Pay attention to the signals that benefit you, shake off the ones that don't, is my advice.

She probably didn't know how to react cause you took her out of her comfort zone. Forget the mixed signals you got her to wait for you and you got her number...keep doing what you're doing and you will prob get what you want.