One piece of advice that hasn't been mentioned yet is that the more miles you go per day, the more calories you need which is balanced by the fact that some people (I'm one ) lose appetite when hiking long miles.

My usual: oatmeal with nuts and fruit for breakfast, midmorning snack granola bar, lunch bagel and meat or peanutbutter and dried fruit, midafternoon snack trisket or chips or cliff bar, dinner 1/2 c couscous or 1/3 c bulgar or one package ramen or 1/2 c rice (before cooking, I use Jasmine) with protein and flavoring and olive oil and two fig newtons.