This information is off the web site for the USDA Food Safety Inspection Service. There's a lot more information available - including a freezing timetable—so we urge you to visit their site for the complete details. Here are a few points we felt were worth repeating:
Refrigerator - Freezers—If a refrigerator freezer can't maintain zero degrees or if the door is opened frequently, use it for short-term food storage. Eat those foods as soon as possible for best quality. Use a freestanding freezer set at zero degrees or below for long-term storage of frozen foods.
Freeze Rapidly—Freeze food as fast as possible to maintain its quality. Rapid freezing prevents undesirable large ice crystals from forming throughout the product.
Packaging—Proper packaging helps maintain quality and prevent "freezer burn". It is safe to freeze meat or poultry directly in its supermarket wrapping, but this type of wrap is permeable to air. Unless you will be using the food in a month or two, overwrap these packages as you would any food for long-term storage using airtight heavy-duty foil, (freezer) plastic wrap or freezer paper, or place the package inside a (freezer) plastic bag.
Nutrient Retention—The freezing process itself does not destroy nutrients. In meat and poultry products, there is little change in nutrient value during freezer storage.
Freshness and Quality—Freshness and quality at the time of freezing affect the condition of frozen foods. If frozen at peak quality, foods emerge tasting better than foods frozen near the end of their useful life.
Length of time—Because freezing keeps food safe almost indefinitely, recommended storage times are for quality only.
Refreezing—Once food is thawed in the refrigerator, it is safe to refreeze it without cooking, although there may be a loss of quality due to the moisture lost through defrosting.