I have an interview at Whole Foods Market, what should say?

Im 18, and I live in Baltimore, MD. Im pregnant, single, live alone, and i have bills out the ***... i am in need of a job reallllllly bad. so i have an interview monday, and i jus want to ace it, wit no questions about it. i want to leave, knowin i got that job!!! lol, but seriously, what kind of traits, or requirements are needed for a cashier position at a market. i know the basics, but i need a little more to spice it up a little, so they can b intrested!!! sooo please help me!! THKS, i really appreciate it