You can not always prevent freezer burn, but here are some things to help. 1) Set your freezer to 0°F and use a freezer thermometer. 2) Never put hot food in the freezer. 3) Use freezer-grade materials and containers. Use freezer paper and buy that freezer zip-lock bags, not the cheap thinner ones. 4) Thicker food, like casseroles, should have several layers of protection. I do a complete plastic wrap and two layers of aluminum foil or freezer paper. 5) Keep as much air as possible out of the storage containers—flatten that zip-lock bag. 6) Leave some room for air circulation around packages and use smaller packages. 7) Keep track of how long things have been frozen.