If you don't have an ceiling fan it is a very good idea to fix it for the following advantages below:
Cooling: the ceiling fans can give good cooling and make you feel 3 to 8 degrees cooler when you are under it. Thus you have to rely on the air conditioner very less. The ceiling fan produces an wind chill effect by pushing the warmer air away from your body at higher speeds.
Heating: Yes, the ceiling fan can be used in the winter for getting a little warmer. The hot air always rises up. so when you turn on the ceiling fan at the lowest speed setting. the fan pushes the hot air down.since the fan is rotating at an very slow speed there is no windchill effect and you actually feel more warmer.