When fruits and vegetables are in season, they tend to cost less. Often, grocery stores will run sales on what's in season because they know customers expect certain fruits and veggies at certain times of the year. As an added bonus, when things are in season, they taste better.  In fall, look for produce like pumpkins, winter squash, cabbage, and apples. In the winter, opt for winter squash, cabbage, and other root vegetables. Springtime is great for produce like beets, leafy greens, spring onions, and asparagus. Summer is a good time for watermelon, corn, and berries, just to name a few. You'll likely notice the cheapest produce prices in summer. Also, because produce is cheaper this time of year, you can buy extra and freeze it or can it yourself. While you may prefer fresh fruits and vegetables, you can often save money by opting for frozen or canned instead. These options have the same health benefits, though be sure to pick ones that don't have added sugar or salt. Check your proteins, too. Frozen chicken may be cheaper than fresh, and canned salmon and tuna is likely cheaper than fresh fish. Most grocery stores run weekly specials, which you can learn about through their weekly ads. When something is on sale, that's the time to stock up on it. Most protein can be frozen and saved for later, for instance, so if your store is running a sale on boneless, skinless chicken breasts, buy some to use and save for later. You probably already know to check for the lowest prices on the items you're buying. However, you may get stuck in a rut buying a certain brand and assuming it's the cheapest because it always has been. However, be vigilant, as prices change all the time. Occasionally there is a sale on a certain package size, or a discount on a run of product that changes what is the most affordable option.   Look up and down, as grocery stores tend to put the most expensive items at eye level. Keep an eye on store brands-- they tend to be cheaper. While buying in bulk can come with a higher price upfront,...

TL;DR in Vietnamese:
Chọn rau quả đúng mùa. Xem giá trên các sản phẩm đông lạnh và đóng hộp. Để ý đến các món hàng giảm giá hàng tuần. Luôn luôn so sánh giá cả. Mua thực phẩm với số lượng lớn. Sử dụng thẻ giảm giá. Nếu ở Mỹ, bạn có thể đăng ký tham gia SNAP (chương trình trợ cấp bổ sung dinh dưỡng) hoặc WIC (chương trình dành cho phụ nữ, trẻ em và trẻ sơ sinh). Tìm các chợ phiên nông dân hoặc các nông trại ở địa phương.