Welcome aboard!

The first tip; consult your doctor (or better yet, a doctor who also backpacks and is familiar with what you’re up against.) Since you don’t mention it, I’m assuming your weight is not an issue.

After that, Colin Fletcher and Chris Townsend (a worthy successor to St. Colin) both said it best: the best way to get in condition to haul a load on a trail is to haul a load on a trail. As with any other training program, start light and work up (or down, if you choose the ultralight path.)

Seriously, if you haven’t already replaced your gear or selected a new set of gear, try to lean toward light gear. (It’s mostly identified as “fast and light,” but there’s no inherent link between the two. I’m slow and light, myself.) There really is some good stuff out there, and not all of it requires a second mortgage on the house. I’ve moved steadily toward a lighter pack over the last 5 or 10 years, and am pretty well settled on a set of gear that has me carrying about sixteen pounds for a two-night warm weather trip in Ohio, and eighteen or nineteen in weather down to about 35 degrees. (Since you’re hiking in the South - Georgia, I assume from your post - that’s essentially year around for you.) The lighter load should help prolong my knees, and allows me to hike all day without collapsing exhausted into camp. (Hiking toward exhaustion also leads to bad judgment, which combined with other physical ailments can put you in trouble before you realize what happened. I’ve written a short description of how I selected my current set of gear; send me a PM if you’d like me to email it to you. (Just remember: I can mislead you with the best of them!)

Also, remember that you don’t have to do “hero treks.” There are many other places besides the AT to hike. (I’ve got a 35-mile trail about 5 miles from me, in the midst of the Dayton-Cincinnati metro area, where I can spend two or three nights.) By choosing the off-seasons, you can even simulate a backpack trip at a state park, using the public campground when it’s not going to be crowded. At 68, I’m at the point in my life where getting out, hiking, and sleeping outdoors are enough; they don’t all have to be adventures with great scenery.

Hope this helps get the ball rolling. If there’s anything folks our age enjoy more than chasing those crummy kids off our lawns, it’s giving more advice than you need.