I've gotten old and have bad knees, but in my 20s I loved backpacking.
Three things:
1) Read
A Walk in the Woods, by Bill Bryson. Funny as hell account of an attempt to hike the Appalachian trail.
2) Check out The Complete Walker, by Colin Fletcher. It's pretty much a how-to guide for backpacking. An early edition of that book got me into the hobby. I know it's been updated several times... it may be out of date with regard to gear, but worth taking a look anyway (I STILL have my Svea stove and it works great nearly 40 years later.... Last time I used it was at last year's track days.).
3) Do NOT tell people you're out hiking the Appalachian Trail if you're really jetting off to South America for a secret canoodle with your lover. That never ends well.
