It varies greatly. I have a typed up list of everything that I keep in my refrigerator and pantry that I print out a few days prior to going shopping. Then I take and inventory of what I have on hand, crossing out the things that I don't need.
LOL Um, ovaltine, milk, eggs, bread, limeaide (to make margaritas!), and something for breakfast to bring w/ us to the beach next week...i'm doing minimal shopping! ;)