Backpacks fall into two categories: external, or E-frame, packs and internal, or I-frame, packs.
E-frames are better suited for Florida. They enable you to carry more weight, and that's important in a state where fresh water is in short supply.
External-frame packs also distribute weight better. Contrary to what many think, the hips, not the shoulders, bear the brunt of backpacking. Too much weight on the shoulders throws you off-balance. With a hip belt supporting the load, you maintain your natural center of gravity.
External-frame packs also are better suited for beginners because the external pockets make it easier to pack. And the frame keeps the pack away from the body, which allows air to circulate and keep you cool.
Packs are measured in cubic inches. In general, carry 800-1,000 cubic inches for each night on the trail. If you plan a three-night trip, you need a pack with 3,000 cubic inches. Most packs sold fall into the 3,000- to 5,000-cubic-inch range. A good E-frame pack costs from $100 to $250.
Look for a well-padded hip belt, shoulder straps and a sternum strap. The frame should be made of a high-tech alloy and the pack of nylon, never canvas.
How you pack your backpack could make or break your trip. In general, carry no more than 30 percent of your body weight. For an overnight trip on a Florida trail, a 25-pound pack should suffice. Your heaviest item will be water, so keep it in the top compartment, close to your back. It will help maintain your natural center of gravity.