I think the biggest thing an AT thru-hiker can do to prepare for the PCT is to kill any preconceptions that it will be anything like the Appalachian Trail. Their common ground is that they are footpaths, and that's about it. I've never really been out west, and I want to see the land in its purest form foremost. It's dryer, hotter, colder, higher and lower, and I'm looking forward to something other than the long green tunnel
The PCT is a trail that extends 2,600 miles from Mexico to Canada. It crosses through every major ecosystem type found in the US from the low hot deserts to alpine tundras and snowfields, and cuts through California, Oregon, and Washington.
I've got a slightly larger pack than I had on the AT, a Mystery Ranch 12 bar. I want to be able to carry as much water as I need and actually eat well on this trip. On the AT, I could never carry enough food. My packs' load capacity maxed out at about 30 lbs. (Granite Gear vapor trail) and sometimes it was hard enough loading 4 days worth of food into it, much less 7-12 days worth. My pack will be heavier but I'll make up for it by getting better nutrition and getting stronger this time.