Chicken's versatility and low cost make it an easy option for cooks, but loading up at the supermarket has a potential downside. Chicken is highly perishable, so unless you freeze it or cook it within the first day or two you'll run the risk of losing your investment. Most forms of spoilage in chicken are obvious to your senses, so it's not difficult to recognize when the bird has gone bad.
The Sniff Test
When chicken is fresh or newly thawed, it should have a very light, clean smell. It might be disconcertingly "chicken-y," especially if you've purchased a large bag of chicken pieces with skin on and bone in, but smells of nothing more than chicken. If spoilage bacteria are present, that relatively clean smell rapidly gives way to more assertive odors reminiscent of old running shoes and memorably funky cheeses. Even mildly whiffy chicken is well on its way to deterioration and should be discarded.
Touch and Sight
If your nose can't clearly decide the question, call on your other senses. It's not uncommon to see thin, watery liquid pool around your chicken pieces -- they're often water-cooled or brined during processing -- but if those fluids appear thick and mucus-like, it's usually a sign of spoilage and bacterial activity. If you're still uncertain, touch the chicken in several places with your fingertips. Fresh chicken is dry, if skin-on, or just faintly moist if it's skin-off. If it feels slimy to the touch or tacky and sticky, it should be discarded. Don't call your sense of taste into play. Even a small mouthful of dubious chicken can potentially make you ill.
The Undetectable Threat
Spoilage bacteria announce their presence pretty clearly, but the same can't be said for the dangerous or "pathogenic" bacteria that cause food-borne illness. Testing regularly finds a veritable rogues' gallery of pathogens in chicken -- E. coli, Staphylococcus aureus, Campylobacter jejuni and salmonella among them -- so it's safest to assume that any piece of chicken in your fridge is contaminated. Rinsing the pieces under cold water won't help; in fact, if anything, it splatters bacteria widely around your kitchen and increases the risk of infection. Instead, observe basic food-safety rules. Keep your chicken refrigerated until mealtime, and then cook it to the USDA's recommended internal temperature of 165 degrees Fahrenheit.
Cooked chicken is typically safe for three to four days in the refrigerator, or approximately twice as long as raw chicken. It should be cooled and refrigerated within one to two hours of being cooked for maximum quality and safety. Make sure your fingers, utensils and work surfaces are scrupulously clean when you package it for refrigeration, because you can easily re-introduce harmful bacteria at this stage. For example, if you've handled deli meats on the same cutting board, you might introduce Listeria monocytogenes, which, unlike most other pathogens, flourishes at refrigerator temperatures. Discard any cooked chicken that develops off odors, and reheat your leftovers to a food safe temperature of 165 F to minimize the risk of illness.