How do you know what is a good price on an item? Is the brand name on sale still more expensive than the store brand? What if it is, but with the coupon it isn't?
If you get a notebook (3 ring binder, spiral, whatever works for you), you can keep track of what things you buy and what the regular & sale prices are.
Each page in the notebook has it's own item. Put the name of the item at the top. I put the abbreviations of stored I shop at (S = Sams, W= Walmart, etc...) Let me do an example.
Cream of Mushroom Soup
S- 0.78/can Campbells
Walgreen's - 0.20/can Campbells with coupons
Some are blank because I haven't priced that item at that store or because it was way more expensive than the other stores anyway. I also sometimes write a really good deal down, so I know how low I could go (See the Walgreen's entry).
Go to the lowest unit you can (ex - 1.00/oz or 0.59/lb), normally price tags will have that listed, so you just have to take a quick look and decide.
You may want to write down the season in which you bought the item. Especially with fresh fruits and veggies, you may want to buy frozen/canned in the off-seasons.
You also may want to write down sale prices, too.
Whatever works for you, it may take a couple weeks to figure it all out, as well as compile your price book. Well, maybe months if you're like me! And I'm still not done!
If you have a price book, you will know what items are at a good price. And just because something is on sale, it doesn't mean it's the lowest price you can get it at. Sometimes you have to choose to wait if you want to get more for your money (I only buy ground beef at 0.99/lb, and I buy a LOT of it to last until the next sale).
When you shop, bring your price book with you as well as a calculator.