How do you grocery shop?

Many people are seen now with calculators out when grocery shopping to find out how much their total is with tax. More items are on sale, and more and more GENERIC brands of items are being purchased rather than the popular expensive brands. For example, instead of getting "Post; Fruity Pebbles", you may look into getting your local supermarkets Fruity Pebbles that has a 1 or 2 dollar difference in price. Are you more cautious of the price? What habits have you changed when grocery shopping.