Years ago my mother got me started making lists of the things I need when I go shopping (which I rarely do). I refuse to impulse buy. I know all of the "extras" I love.
Have you looked into surplus or salvaged food stores? So the can may be dented, as long as the seal is still good and the food is in date, you can really rack up the savings.
You can do the same thing with big ticket items. There are salvage sites on the internet where you can buy goods that have been declared lost, and an insurance claim paid. They auction off these goods in bulk lots. Ive bought them. Here is an example of what I got for about $400.
Two refridgerators (one standard, one with ice and water in the door)
Three microwaves
Coca-Cola mini-fridge
Four stereo systems
Three televisions
Two DVD players
Two VCRs
Two unassembled bookshelves (each 6ft tall when assembled)
Two office chairs
Alot of nicknacks, tools, and odds and ends like surge protectors, lamps, toys, and CDs.
I kept what I wanted and sold the rest. Made my money back. It was like getting free stuff.