How do you know when you're getting a good deal?

Sometimes it's hard to know if you are getting a good deal. You see the big red tag, clearance sign or the huge SALE sign, and you get so excited and psyched into thinking that you are getting a good deal. But, how do you really know when you are getting a good deal?
I never buy any of the following items unless I can get them at least 50% off...
Laundry Detergent
Dish Detergent
Feminine Hygiene
Diapers
Medicine
Formula
Baby Food
Baby Wipes
Dog Food

ANY meat, I never pay more than $1.99lb- if you buy at the right time and stock up when there is a good deal, you shouldn't have any trouble staying under $2 a pound.

I never pay more than $1.00 for....
Loaf of Bread
Tortillas
Juice
Cereal
Crackers
Fruit Bars
Granola Bars
Oatmeal
Chips
Glass/Floor cleaner

I never pay more than $.50 for the following....
Pop Tarts
Waffles
Pasta Sauce

I never pay more than $.25 for the following....
Frozen Pizza
Frozen Veggies
Refrigerated Dough
BBQ Sauce/MarinadePasta and boxed pasta
Rice and boxed rice
Canned Veggies
Canned Fruit
Toilet Paper
Creamer

I never pay for...
Hand Soap
Pizza Rolls
Aluminum Foil
Zip-Lock Bags
Make-up
Chex Mix
Shampoo
Conditioner
Body wash
Deodorant
Razors
Shaving Cream
Tissue
Toothpaste
Toothbrush
Soap
Candles
Air Freshener
Sour Cream
Creamer

If you always have at least 4 copies of each week's inserts, you should have no problem stocking up when any of the above items are on sale. When you stockpile an item, the hope is that you have enough to get you by until the next sale comes along.