How to Pick Warm Comfortable Sleeping Bags For Camping.

First off it should at least be rated for the lowest possible temperature you'll encounter. You may want to even go a little lower just to be on the safe side.

Obviously the main purpose is to hold your body heat in to insulate you from the cooler air. So the better the insulation holds your body heat in the warmer and more comfortable you're going to be.

Insulation

Down-the filamentous and fluffy layer underneath the feathers. Positives: All being equal down is warmer, lighter, more comfortable, compresses smaller, and can last a lifetime if cared for properly. Goose down is the standard others are compared to. The more it lofts the better it insulates. This is known as fill-power, the higher the number the better it retains heat.

Negatives: Down looses most all of it's insulating properties when wet, takes a long time to dry outdoors, is more expensive short-term, and may require professional cleaning.

Synthetic- These are usually hollow plastic threads that serve to trap warm air. Positives: Synthetic sleeping bags retain heat better when wet, costs less short-term when compared to the same temperature rating as down, dries quicker than down, and is hypo-allergenic. It's usually well-suited for recreational use, but consider your own individual needs.

Negatives: They're bulkier, heavier, less conforming, and can lose their insulating properties after a few seasons of hard use because of breakdown. More expensive long-term.

Shapes/Styles

Child's/Kid sleeping bags- A kid has a harder time staying warm than an adult, so keep this in mind when you're getting them a sleeping bag. A cool summer night can chill a child quickly so consider a mummy bag like the Tigger by North Face to keep them warm and cozy.

Mummy- Provides more warmth for cold conditions and is more compact/lighter when packed. The narrow cut and insulated hood means less air for your body to heat. This bag is wide at the shoulders and narrows down to the feet. The drawback is it restricts movement. That said the Marmot Sawtooth sleeping bag is a good light 3-season 15 Degree down sleeping bag ideal for backpacking.

Rectangular- These sleeping bags are ideal for campground camping because they give you more room to move around in. They're not suited for the winter due to the larger area you have to heat and the open top design. This is the best design for double sleeping bags, usually you can just zip two of the same kind together. Not for weight conscious backpacking and hiking gear enthusiasts.

Semi-Rectangular- A combination of the mummy and rectangular sleeping bags this hybrid splits the middle between room to move and warmth.

Comfort Ratings- The "comfort rating" is the minimum temperature that a sleeping bag is designed for. Of course this is just an approximation as people tolerate temperature differently. If in doubt go...

If you'd like more information on sleeping bags click here for the rest of the article. You may also want to take a look at this related article on how to pick a great camping tent.