Keeping things clean is very important (as mentioned earlier). I have a AD truck and I spent a lot of extra money to get a rust free truck from Arizona and like you I wanted to keep it that way.
The first thing I did was to vacuum out the problem areas (behind the seat and cab corners). LOTS of dust and dirt had accumulated there over the years. I took the doors off, turned then upside down, and used high pressure air to make sure the pinch seam at the bottom was free of dust and dirt. Then there is the front cowls, on the right side there is an access panel on the inside. On the left, someone already cut a hole to put a speaker in. I blew these areas out real well. There was a LOT of desert dirt/dust in all these areas.
Next I will treat the inside surfaces to POR and/or epoxy primer. Problem is I cannot work on my truck for two more years (out of the country on biz). In the meantime I keep it in the garage out of the elements.
Really that's about all you can do. If you drive it in the winter in a state that salts roads it (and every other vehicle) will rust. If you store it in the winter, it won't rust till long after you are gone...
Last edited by mendonjo; 02/02/2013 12:59 PM.