What is the first thing to check when a refrigerator stops cooling?

What is the first thing to check when a refrigerator stops cooling is power supply, thermostat setting, and condenser coils, before calling technician. First, check if refrigerator is plugged in and breaker not tripped, open door and see if light turns on, if light off, check outlet with phone charger and check breaker panel, if power lost, reset breaker. Second, check thermostat setting, ensure temperature controls inside fridge not accidentally set to Off or warmest setting from cleaning, set fridge to 37 degrees and freezer to 0 degrees, if controls set correctly but still warm, listen for compressor humming at back. Third, check condenser coils behind or under fridge, if coils covered with dust, pet hair, and lint, compressor overheats and cannot cool, unplug fridge and vacuum coils with coil brush, this fixes about 20 percent of not cooling cases. Fourth, check door closed properly, ensure door gasket not torn and door not blocked by food, warm air entering causes not cooling. Fifth, check if freezer cold but fridge warm, indicates evaporator fan or damper failure, listen for fan in freezer. Sixth, check for ice buildup on back wall of freezer, indicates defrost failure. If these basic checks do not fix cooling after 2 hours, call technician for compressor or sealed system failure costing 400 to 800 dollars, as sealed system repairs are expensive and often not worth it on older fridges over 10 years.