Write down your number and tell her that you would really like to continue the conversation and if she wants to call you
Bad idea. Have you noticed how many guys just give their phone number left and right. Guess what becomes of the phone numbers...yes trash's best friend. It is better that you get her phone number. That's the real test if a woman is interested and/or comfortable with you or not. If she says no, go to the next Starbucks and start all over again. It is a numbers game.