My experience with backpacking isn't extensive at this point. I have been on 3 trips so far.
I went on an overnight trip to Mt Baldy in the AZ White Mountains when I first got my gear. I found the trip in Backpacking AZ from the Wilderness Press. It was a long drive there so we did not get started until late. We were even later because a swarm of bees decided to attack the car on the way to the trailhead. The first day was mild, not much elevation gain or loss. We had driven from 1200 feet up to 8000 feet I believe (it may be 9000 I don't have the book with me now) so it was slightly harder than it should have been. But altitude has never bothered me much so it wasn't a big issue. The next day saw a lot of climb and the summit itself is off limits as it is on a reservation so we didn't get a "climax" at the top. We rested up and on the way down stumbled across a very nice view slightly off trail and that was what we were looking for. The trail was poorly maintained at points, there were downed trees to hop over or duck under. Looking back, we brought WAY too much stuff for a one nighter. My pack was probably 35 to 40 pounds and Caryn's was around 25-30. I'll get more into equipment I have lightened up on and eliminated in another post sometime.
My second trip was the Rae Lakes Loop which we did not complete due to Caryn getting ill (she blames GU) and again heavy packs. More details on that trip are in an earlier post.
The third trip I went on was from Olmstead Point in Yosemite to Yosemite Falls and down to the valley floor. That trip went much better than the other two. There wasn't too much up hill (although there was plenty), but the down hill hike from Yosemite Falls is Brutal. I went on that trip with my siblings and we were able to split the load pretty well. We brought some "luxuries" even and my pack was 30 pounds for a 3 day trip.
Other than those overnights I have hiked to the top of Half Dome and Yosemite Falls from the valley floor. Both hikes were tough, but I managed both of them as good as anyone else. I know this isn't enough experience to go out and attempt the JMT, that's why I am giving myself 2 years of training hikes and trips. I have 12 backpacking trips planned out from now until JMT, and I plan on doing a few others when the opportunity arrises. (Overnights in Sespe and the Santa Monica Mtns for example) The dates are loose, but I am going to stick to them as much as possible. Most of these trips I found in Backpacking CA from the Wilderness Press.
1) 9/24-25 - 1 night to the top of San Gorgonio Mt via the Vivian Creek Trail. This will be a good one for uphill training and altitude training.
2) 2/18-19 - Devil's Canyon in the San Gabriel Wilderness. A winter appropriate trip.
3) 4/1-4 - 3 nights in the Sespe Wilderness, this is local and I can bring my dog.
4) 5/12-14 - San Bernardino Traverse. 21 miles across the San Bernardino Mtns. Good for the distance I want to cover on the trail.
5) 6/22-27 - The San Jacinto Traverse. 55 miles of the PCT, this is a hard one, but who ever said I was doing this because it was easy.
6) 8/9-18 - The High Sierra Trail. 68 miles across the Sierra Nevada West to East. part of this is the end of JMT as well.
7) 11/10-12 -Angeles Crest. 2 nights on the PCT.
8) 1/12-15 - Joshua Tree National Park. Another winter appropriate location, this may change to an AZ desert hike.
9) 2/11-12 - Big Santa Anita Loop. An overnighter nearby.
10) 4/6-8 - Sespe once again.
11) 5/6-7 - East Fork of the San Gabriel River
12) 6/20-26 -Rae Lakes Loop. This is the direct warm up hike to JMT.
13) 8/7-9/4 - John Muir Trail (exact date is subject to permits)
As I said these dates may change to accommodate schedules, but all these trips will be taken around their scheduled times. These are a mix of easy overnighters to refine gear selection and camp skills. I am not a moron when it comes to the outdoors by any means, but learning what I use and don't use will help to keep my overall pack weight down.
Along with these overnight trips I will be hiking mainly the Santa Monica Mountains in day hikes because they are close. I plan on taking my pack most of the time so the weight becomes a part of me. There are endless trails in the Santa Monica Mountains so I can really hike any distance I choose. As my planned pace for JMT is going to be relatively slow (8-12 miles a day [itinerary to come later]) I am going to shoot for getting used to 15-20 miles out here on day hikes.
I feel that this schedule will get me through the trail. When my Mom decided she wanted to hike Mt Whitney she made a plan and stuck to it. She succeeded. This is my plan and I am sticking to it.