The best way to ask a woman out:

1. Most importantly, remain cool, don't show that you're nervous and create an awkward situation.
2. Don't make the girl feel like you're putting her on the spot.
3. Just about when you're ready to leave, turn around and say "Oh hey, you seem pretty cool, oh and you have a phone, let's talk later, what's your number?"
4. As she's writing down her numver, also get her email.