Down's Fill Power

When looking for a down comforter, check the amount of fill -- the number of cubic inches per ounce of down. The higher the fill number, the warmer the comforter and the better the quality. Standard fill is 500 to 550; high quality is 600 to 700. Above 700 is unusually high and very expensive.

Finding the right weight: Comforters are also manufactured in weights by season and region. The lightest weight (sometimes referred to as summer or "southern" weight) is about 26 ounces for a queen size; a winter or "mountain" weight queen size is heavier, at around 54 ounces.

Shell construction: Even though duvets are encased in duvet covers, the actual duvet includes a fabric shell, also known as ticking. It should be lightweight and made of down-proof fabric.

Stitching on duvets is important since down needs room to loft, or puff up. Most comforters are stitched with baffles, channels, or other stitching lines to keep the down evenly distributed throughout the comforter. Without it the down can shift and bunch up, making it less effective for warmth. All comforters, regardless of stitching patterns, should be shaken each morning to fluff and even out the filling.