Could you please explain the procedure to be adopted in Kashering a microwave oven?

The microwave should be cleaned thoroughly and should not be used for 24 hours prior to koshering. A bowl with water should be placed inside and it should be boiled for 15-20 minutes. For safety, extreme caution should be taken upon removing the bowl with water. This method of koshering applies only for a microwave which does not have browning.