When your fridge malfunctions, you need answers quickly. Otherwise, you could end up losing hundreds of dollars' worth of food. This list of possible causes and solutions will help you analyze your problem. See also How to Refresh a Smelly Refrigerator, How to Fix a Leaking Refrigerator, How to Repair a Clogged Ice Maker and How to Fix a Refrigerator That Cools Poorly.
If the fridge won't run, first check the power cord, and the reset the circuit breaker.
Check for thermostat problems. It could be off or won't cool properly (too warm, too cold). If it can't be fixed with a simple adjustment, call a professional.
Check for coil problems. The compressor can overheat due to dust buildup on condenser coils. If so, vacuum the coils. If there's ice buildup on evaporator coils due to bad defrost heater, call a professional. If there's a squealing sound inside the refrigerator, it's like a failing evaporator-coil fan. If so, call a professional.
If there's frost buildup in the freezer, this is due to a bad defrost heater, in which case you should call a professional.
Realign the water tube if it's out of position. It could cause problems with the ice maker.
Replace any worn-out gaskets.