If you want to keep to a tight food budget when food shopping, realize that grocery stores spend a lot of effort sucking you into buying more food than you'd actually intended. Your shopping habits are the result of great gobs of marketing money spent to disengage your practical brain from the moment you enter a store.

I often feel a sense of otherworldly surrealism in first world supermarket grocery outlets. Soft, slow music plays and the lights are bright, so you feel awake but relaxed. Grocery stores have no windows and no clocks, just like a casino, so you lose any sense of the passing of time. Simple food staples are placed at foot and shin level, while pretty, expensive, heavily packaged goods are found easily at elbow and eye level.

Frequently purchased perishables like milk, eggs, butter, cheese, meat, and bread are located along the back and sides of the store - so you have to run through non-essentials like chips, sodas and cookies to get what you actually need.

Shop the Edges of the Store

The best way to save money while running the grocery store gamut is to know exactly what you need to buy, and work your way around the margins of the store. If you start with the produce aisle (usually to the far left or right), you can work your way around to the dairy, eggs and meat in the back, and sweep though the bread on the far wall.

After you've hunted down all the staples you need along the store margins, take a look at your shopping list and see what you've missed. If you need canned goods, head straight to the canned food aisles. Tortillas are usually on an end cap and you can sweep past those on your way to finish up with your last few items. Make a point of trying to walk through as few aisles as possible.

Other Frugal Shopping Tips

• Don't ever go food shopping hungry.
  
• Try to make a list first, so you can get exactly what you need and get out.
  
• Try not to shop with children!
  
• Avoid the aisles that tempt you the most. If you know you like packaged snacks, don't even go down that aisle. Personally I find myself sucked into buying new cleaning products, so I try to stay away from the cleaning aisle. I don't like soda, so that aisle is safe for me to transit. Your mileage may vary.
  
• Use a price book and shop the sales. If you can stock up on certain non-perishables, you can stay away from the store that much longer.
  
• Remember that even if you only need "one" thing, chances are good you'll walk out having bought other stuff. Staying away from the store will keep those small impulse purchases from adding up.
  

As my husband says, try to grocery shop like like a SWAT team. In and out, without getting sidetracked!

Amazon has lots of books with this theme:

Joyful Momma's Guide to Shopping & Cooking Frugally: Tasty Tips for Saving Money from the Grocery Store to the Dinner Table

2012 Family Guide to Groceries under $250 a Month