Thinking about doing the entire Appalachian Trail or just a longer section?
You should get yourself the Appalachian Trail Thru-Hike Planner from the Appalachian Trail Conservancy. This books provides a single place for you to get pretty much all the information you'll need for hiking the entire trail or just some sections of it. It offers hints, tips and ideas for planning and executing your trip.
In its seven chapters this book makes you think about what you really need to consider when you are planning a thru-hike of the Appalachian Trail. What I am going to do about money? What about resupplying as I hike? How do you stay motivated when hiking for six months?