Of course there are many different ways to approach a woman, but this is an example of an easy/safe way.
Compliment her on something she is wearing. "I like your watch, where did you get it?"
She might respond in a few ways, either she will be happy that she is being approached, and respond enthusiastically where you can easily ask her what her name is and take it from there.
She might say "Thanks" and turn around. It is not embarrassing to be "rejected" like this because it was a harmless compliment. It's not like saying "Hey baby whats your number" and getting shot down.
She might say "Thanks" and wait for you to take the lead, sizing up your confidence and see what you are all about.

Holy shit. A complement huh? Who would of ever thought of that? Nobel Prize money here boys.

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They call me the cat whisperer, cause I know exactly what the pussy needs.