How to ask a girl out?

I know this girl who is like a bestfriend and Iv seen her alot in the past three months, at the most twice a week. I drop by her house to see her even if it's for five minutes and we have become closer. Although we are close friends, we are both attracted to each other and i like her alot. Iv once asked her if she wanted me to buy her coffee and she thought it was sweet but she couldn't because she has finals and she didnt think she will have time but she said she will text me when she wants to go with me to Starbucks. She hasn't texted me yet but Iv visited her and we talked by her doorway a little then we just stood there saying nothing so I gave her a hug and a kiss on the cheek because she was going out with her friends later and as she smiled she says " where am I going now" I want to ask her to hang out with me but I don't want to make it sound like a date. Please help?