You’re already eating at home instead of going out to restaurants, and you’re already making a shopping list and trying to stick with it, but you could probably do better. The average American spends almost 8 percent of his or her income on groceries, and grocery stores are doing everything they can to get more of your money — after all, it’s a $465 billion business. One trick you can use to make sure you follow your list and stay on budget is to shop when you’re in a hurry. Have only 30 minutes before you have to pick up the kids or get your hair cut? Grab your stopwatch. Ready, set, shop!