It's best to get fresh dried lentils. It's a bit tricky to know how fresh the lentils are when you buy them in a bag. However, if you go to the bulk section of your grocery store, you'll find more options, and the chances are those lentils are more fresh than the ones that are already bagged for sale. After you buy your lentils, and are ready to prepare them, be sure to give them a good rinse, and remove any stones, brown, or damaged lentils.