Eggs
When something starts pecking its way out of the shell, the egg is
probably past its prime.
Dairy Products
Milk is spoiled when it starts to look like yogurt. Yogurt is
spoiled when it starts to look like cottage cheese. Cottage cheese
is spoiled when it starts to look like regular cheese. Regular
cheese is nothing but spoiled milk anyway and can't get any more
spoiled than it is already.
Mayonnaise
If it makes you violently ill after you eat it, the mayonnaise is
spoiled.
Frozen Foods
Frozen foods that have become an integral part of the defrosting
problem in your freezer compartment will probably be spoiled - (or
wrecked anyway) by the time you pry them out with a kitchen knife.
Meat
If opening the refrigerator door causes stray animals from a
three-block radius to congregate outside your house, the meat is
spoiled.
Lettuce
Bibb lettuce is spoiled when you can't get it off the bottom of the
vegetable crisper without Comet.
Canned Goods
Any canned goods that have become the size or shape of a basketball
should be disposed of... Carefully.
Carrots
A carrot that you can tie a clove hitch in is not fresh.
Wine
It should not taste like salad dressing.
Potatoes
Fresh potatoes do not have roots, branches, or dense, leafy
undergrowth.
Chip Dip
If you can take it out of its container and bounce it on the floor,
it has gone bad.