There are 3 ways to serve sake; warm, room temperature or chilled.
Sake can be warmed in various ways. The most common is in a professional sake warmer which is used in many Japanese restaurants. Another way to warm sake is to microwave for 20 to 30 seconds and the most ideal way is on the stove in hot water until the sake is warmed to the temperature you desire. Most premium sake are consumed at room temperature or chilled much the same way as white wine.
Sake should be handled in the same manner as wine. It should be stored in a cool dry dark place where no direct sunlght can affect the delicate balance.