Perhaps you'd benefit by having a calendar in your kitchen. If opening the refrigerator door causes stray animals from a three-block radius to congregate outside your house, the meat is spoiled. Fuzzy and hairy looking white or green growth areas are a good indication that your bread has turned into a pharmaceutical laboratory experiment. Flour is spoiled when it wiggles. Bibb lettuce is spoiled when you can't get it off the bottom of the vegetable crisper without Comet.
Romaine lettuce is spoiled when it turns liquid.
Any canned goods that have become the size or shape of a softball should be disposed of. A carrot that you can tie a clove hitch in is not fresh. Raisins should not be harder than your teeth. If it looks like it is ready for planting, toss it. If you can take it out of its container and bounce it on the floor, it has gone bad.