Generally start with 'Hello.' Then introduce yourself. If she is remotely interested or in some cases just being polite, she will say Hello and introduce herself. If she just says 'Hi' and walks away, then you know 0 interest. From there is just basic conversation. In a grocery store would be difficult to keep going with any sort or relevance, but try to be tactful. If you are in the produce aisle maybe mention a recipe you saw for a citrus fruit salad while youre picking out the items. Just don't look in her cart and mention what nice melons she has.
