I did part of the JMT last year as a warm up for the AT.
I learned alot from this experience which elped me successfully complete te AT.
Yes, keep pack weight down, but start with the pack its self. I did the JMT with a pack that weighed close to 7 lbs empty! yikes
Elevation-this doesnt really apply to the AT but when you start the JMT, the elevation will kill you. I did about 14 miles the first day and nearly faineted when I took my pack off. My advice-take it slow the first few days while you adjust to the altitude.
terraim-What killed me on the JMT wasnt just the climbs but the loose rocks on the climb. I ended up having to leave the trail in the end due to blisters which were caused by a heavy pack, green feet, and the loose gravel; take care of the feet.
weather-I had great weather on the JMT and the AT but be prepared for cold, wet weather. This, to me is the ultimate weather challenge. I can deal with cold, I can deal with wet, but wet and cold, thats the tough one.
Agree with other poster=you should have contigency plans. I had to bail out and get a ride into mammoth which is very easy. I would have gone back to the trial from mammoth but ran out of time.
jalan jalan