When selecting a sleeping bag there are several things to consider: the type of camping you will be doing - car vs. backpack; the type of climate you will be camping in; and down vs. synthetic. Compared to synthetic fills, down offers more warmth for the weight, better compressibility, greater durability, and a sinfully luxurious feel. It's also more expensive, and it's useless when wet. Now, some people contend that if you properly stow your bag in a waterproof stuff sack and keep it tucked in your tent when its raining, the wet-weather performance of any insulator becomes a non-issue. Almost but not quite. If you live in a perpetually wet climate such as the Pacific Northwest, or the humid south, you can be as careful as possible keeping rain and snowmelt away from your bag, but high humidity will still make it feel damp.

The bottom line here is that if you like to hike in rain forests or sleep near waterfalls, or if you live a generally damp part of the country, you're better off with either a synthetic bag or a down bag with a water-resistant shell like DryLoft.

Which brings us to one of the most important before-you -buy factors: the shell fabric. At the economical end of the spectrum, there's polyester and nylon taffeta. Nylon taffeta is known for its abrasion resistance, while poly taffeta stands up to the sun's UV rays better and absorbs less water than the nylon version.

A step up in terms of cost and protection from the elements is microfiber, a generic term used to describe a tightly woven fabric with good wind and water resistance, as well as breathability. But if you spend a lot of time sleeping tentless under the stars, you probably want to invest in a DryLoft-sheathed bag.

DryLoft will bump up both the price and the weight of a bag, but it's windproof, breathable, and more water-resistance than other shell materials. We found that DryLoft increases a bag's warmth by about 5° F. While DryLoft doesn't eliminate the need for a bivy sack or tent in wet conditions, it renders moderate wetness, like tent condensation, harmless. A tip about DryLoft bags: Stuff them foot-end first, otherwise they balloon up because air gets trapped inside.

Some Sleeping Bag Tips:

• Make sure you can care and do care for sleeping bags as detailed in their instructions. Most bags need to be kept "uncompressed" (lying flat (under a bed on a wardrobe) or hanging, not in their compression sack.
• Consider buying a sleep bag liner. It takes up a bit more room than a single bag but it worth the space but it can keep the temperature in the bag more comfortable, and it protects the sleeping bag. This means the bag will need less washing and that the liners can be washed more often without damaging the sleeping bag. The liners are also easier to air, dry and wash while camping.
• Most of heat loss is through the base of the bag (the bit you lie on) as the filling is compressed so make sure you have a good ground mat.

References:
Essential Gear Manual by the Editors of Backpacker Magazine; and, "Information on Sleeping Bags and Comfortable Sleeping While Camping" by Victor Epand at Content4Reprint