Purchase a double-strength corrugated cardboard box or foam ice chest.
Line the bottom of the box with dry ice or frozen gel packs. Dry ice should be wrapped.
Place wrapped food into the box on top of the cold source. Add more dry ice or frozen gel packs on top of the perishables.
Add packing peanuts or crumbled paper to fill in any air spaces around the food. This will keep the food cold longer.
Seal the box with packing tape.
Wrap the entire box in 2.75 mil polyethylene film or plastic wrap for extra protection, if desired.
Label the package with the correct name and address. Use permanent marker.
Write "Keep Refrigerated" and "Perishable" on the box. If using dry ice indicate this on the box so that the recipient knows what to expect when the box is opened.
Place the shipping label on the outside of the film if the box is packed in 2.75 mil polyethylene film or plastic wrap .
Mail the package at the beginning of the week so that it does not sit in the post office over the weekend. Most of the times you'll want to pay the extra expense of overnight shipping.