Forgot to mention- if you are not at your ideal body weight, start reducing your eating. Again, go to a nutritionist if you are not sure how to do this and stay healthy. I have never had a weight problem so I always forget this.

I would also start doing a lot of car camping. That way you can get used to sleeping on the ground and living on the ground. Getting in and out of a small backpacking tent when stiff is interesting! Anyway, there are a lot of camping "kinks" to work out (no pun intended) that will make it easier once you actually go backpacking.