Location
Determine where the microwave is to be plugged in. Select your outlet based on the acceptable requirements for each location. A GFI or GFCI outlet is needed if the microwave is located less than 6 feet from a water source such as the edge of the sink, toilet, shower, etc. It is also needed if located outdoors, garages, kitchen counter tops, near laundry, utility sinks, wet bar sinks and near swimming pools.
Validation
Inspect the area chosen. Measure the distance of the outlet from any water source and if more than 6 feet, you can use a regular outlet. On a kitchen counter, no outlet can be more than 4 feet apart and in any other room, it should be not more than 12 feet apart. Do not plug microwave in an extension cord even if it is plugged into a GFCI.
No Exception
Use a GFI or GFCI outlet for the microwave if it has a public access and in is in a commercial or industrial setting. This includes hotels, restaurants, coffee shops, lunch rooms, smoking areas, etc.
Safety
Press the test button of the GFCI before use to ensure it is functioning correctly. The reset button pops out to indicate that it is in working condition. If this does not happen, it is defective and needs to be replaced. Push the reset button to restore power and your microwave is ready to plug in. As of 2005, test buttons are required on all GFIs. If it does not have the test button, the GFI has to be replaced.