I use a little technique I got from this forum several years ago. Start with cold tires, empty truck and inflated to door sticker pressure. Find two pieces of something thin, flat and straight. Place them under each end of the tire where it contacts the pAvement. Measure the distance, making sure to square it up. Add whatever load you're going to have and repeat the process adding air until you get back to the first distance.
It has worked well for me. Tires wear evenly, ride is good and it handles well.