$183*The more trips you make to the store, the likelier you are to buy on impulse because you see more tempting items. About two-thirds of purchases are unplanned; cut that in half to save $143 a month (if you spend $100 a week on groceries).Stop drinking bottled water and instead buy a filter for your faucet (about $34, plus $25 for replacements). If your family consumes 12 gallons a month, you'll save about $15.Out-of-season produce costs 20% to 50% more than it does when it's in season. For a list of what's in season when, go to fruitsandveggiesmorematters.org . Estimated savings: $7 a month.Organic produce costs $1 to $2 more than the conventional kind. Cut your pesticide intake by going organic on the dirtiest produce (apples, lettuce) and conventional on the cleanest (kiwi, tomatoes). For a list of clean and dirty fruits and veggies, go to foodnews.org . Savings: $18 a month.