Help is on the way
First, get yourself a copy of Christine Jette's book, Professional Tarot: the business of reading, consulting & teaching. Skim it for your interview, then read and re-read it.
Any good interview has one objective; impress the might-be-boss with your appearance and confidence. Clearly define how you prefer to work, what you need for facilities, determine what portion of your fees that you will keep and what will be shared with the establishment, have a code of ethics & practice written out. Your decks and accessories should be professionally packed and carried -- don't pull them out of your pocket or purse. Be prepared to give a sample reading.
Remember, don't give away your profits. You will be bringing traffic to the store, helping to sell books and other items. If this establishment is a book store with a coffee shop, you might want to set up near the coffee shop, that will bring added business to them also. Determine if there are other readers of tarot that practice there, what hours & days have the most traffic and whether there are "events" held there. Events are often advertised and there is no reason why you can't have a small share of the advertising that the store carries out. Good luck, keep us informed, and don't be afraid to ask more questions -- this forum is very supportive. Dave.