When we first started backpacking we were carrying way too much food (about 25 lbs between us). We started searching the Web & talking to friends for tips to lighten up. Here are some of the things that have helped tremendously:

Dehydrator:

We bought a dehydrator at Kmart for $30. It's been wonderful. We dehydrate a jar of spaghetti sauce for pasta (it turns into a leather roll like a fruit roll up), we make our own jerky (much cheaper & better quality than store-bought), we dry fruit (apples, apricots, strawberries, pineapple), fruit leather (strawberry, kiwi, etc.), & vegetables (esp. tomatoes).  We even fry up a batch of hamburger with spices and dehydrate (fantastic with pasta sauce!).

Packets of condiments:

Instead of carrying mayo, mustard, relish, hot sauce, parmesan cheese, hot peppers,etc. in plastic containers we take packets which can be purchased at Costco or (wink, wink) picked up at fast food restaurants.

Freezer bags:

Instead of carrying ingredients in there original containers we pre-mix ingredients & carry them in zip-lock freezer bags. This cuts down on weight, trash & the bags have other uses such as holding fish guts or collecting dry moss & twigs for the campfire.

Other tips:

Always pack an extra meal or two just in case.

Cover pot when cooking to save fuel.

Eat fresh or fatty food first so it doesn't spoil.

Eat heavy foods first to lighten load for rest of the trip.

Try to avoid really spicy foods. Indigestion is no fun.

To keep critters out of camp keep food stored away & pick up spills. Never sleep with food (or other attractive items like toothpaste, gum, etc.) in your tent -- hang it in a bag from a high tree limb or put it in a bearproof container stored away from camp).