There are three ways heat can move or be transfered from one place to another: convection, conduction, and radiation. Convection means moving in currents of air or water, so you must prevent any currents of air or water coming in contact with your material. Conduction is when heat moves directly through the molecules of a substance like a metal or liquid. Metals like copper and aluminum are good heat conductors. Airy things like foam, feathers, cotton balls, fur, plastic, and dry wood shavings are poor conductors. Radiation is like the heat from the sun, or from a hot coal. Think of radiation as "rays" like from a ray gun. But they are heat rays. You can stop heat radiation really well with a mirror. It just reflects it right back. So now that you know these facts, think of things around the house that fit the bill. Well, for radiation you might wrap your thing in aluminum foil--shiny side in. This will keep in any radiant heat. Then surround it with something light and fluffy that is around your place. Maybe some fur or feathers or styrofoam. Put the whole thing in a box so that no air currents can get to it. And you have prevented all the ways that heat can move.