Read the links and follow the advice. We'll add a few checklists and doable actions but you should be able to cut your food budget from 33% to 50% following what is below.
It can be inexpensive AND healthy
The Poor Man Diet need not be unhealthy. It is just a matter of using your limited money judiciously. For most people, it is more of a question of how can I eat reasonably economically, as they have other things they would like to spend money on or retirement contributions they want to make.
Is it worth the time?
The return for your extra time in shopping cheaply (such as time to collect coupons) is well in excess of what most people make per hour on their jobs (after tax).
Pre-washed and prepared items generally cost $5 for every three minutes worth of work for washing.
Formulate a plan, for greatest effectiveness
A written plan, kept in an accessible place, forces one to think ahead. You'd identify stores to go to, list what is cheapest per amount of nutrition in each category, and then implement the other strategies listed below.
It's vital to keep this all easily retrievable
What you learn and gather most often gets lost and goes into disuse. Keeping a three ring binder with tabs to separate is a great way to keep it all referenceable. It is immensely worthwhile to spend the small amount of time necessary to set this up, as it saves many hours and many dollars over time. (Yet people resist doing this because it "takes too much time" or "I'm too busy" - the irony is that it saves time, not takes time, over the long term - so we've got to use adult thinking here!)
References to use to get smarter
Being smart means putting some effort into what makes sense and has a payoff to learn; it is the only way to get smarter.
What to eliminate:
Obviously all expensive items and low nutrition items per dollar.
All expensive coffee drinks
A place to put things:
Buy an extra freezer if possible.
Large, closable containers for bulk, such as cereal and beans and nuts.
At the right place.
Food discount stores, CostCo, Sam's Club. Dollar stores are a great source.
Make a simple price book to determine which store near you has the best prices. The easiest way to do this is to identify the fifteen to twenty-five most common things you buy at the grocery store.
Use the discounts
Use coupons, if possible go to stores where they double the coupons.
How much does it cost?
Average for family of 4: $709/month. Cutting out the excess costs and the unhealthy foods, it can be as low as $400 - $500 a month.
Keep your weight slightly below what the chart says is your best weight. Eat lots of fiber and eat often in small quantities and you'll never be hungry.
Food preparation time
The recipes and dinner options should meet 4 criteria: Cheap, Healthy, Easy to Make, Easy preparation and clean up.
What to buy
Eat plain yogurt, add fruit yourself.
Buy frozen in bulk.
Buy cereal from the dispensers, not in a box.
Eggs are great and cheap.
Hot air popcorn popper. High fiber, low fat (if you don't add butter and just use flavorer)
In regards to the calorie/ cost ratio, dry beans are perhaps the cheapest food in the world next to rice. Eat Beans.
What to consume
Drink lots of water!
Eat lots of vegetables, they fill you up inexpensively but nutritiously.
Cook in bulk once a week (called batch cooking).
Crock pot that'll fit in the fridge to provide meals.
The Wise Spending Shopping List - Create your own list of items that are cheap, then use it as a checklist of items to buy as you go through the week.
Canned tuna, packed in water, is cheap and healthy.