How to ask out a girl who works in a retail store (famous footwear, clothes store, etc)?

aeroruler
So I was curious as to what people thought was the best way to ask a female store worker out. Is it a necessity to make small talk and figure out if they like you first or can you just be up front and say, "would you like to grab a bite to eat sometime?" while your in the checkout line or something. Also, I am referring to stores that you don't go to all the time where you can be a regular customer.
How to ask out a girl who works in a retail store (famous footwear, clothes store, etc)?
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