Don't buy anything at eye level. Anything at eye level is the highest profit for the store. Buy store brand products if they're used for cooking or will be mixed with other products. For example, brand name pineapple is the same pineapple as the store brand. A pineapple is a pineapple. Do a lot of comparison shopping. Most people have a favorite grocery store and it costs them. Shop the ads and consider stores that you don't normally shop. All grocery stores are not equal.
Being on a tight budget, I have had to cut down on our grocery items. Only buy what is necessary, the basics. I buy most of the no name brand products, they taste the same you are not paying for the fancy names. Look for the weekly specials and get only what you will use. I have found that coupons are a great help, they are in the mail, magazines and I have used many off the internet, some items I have gotten for free. Once a month I add an item or two that is not necessary but have a limit.