Aesthetics
There are many brands to choose from, find one that offers a style and a finish that you like. Most fan manufacturers offer several styles from traditional to modern contemporary, and many offer outdoor models. Keep in mind the scale of the fan for the room in which it will be installed.
Ceiling Heights
The more space between the blades and the ceiling, the more effectively the fan will circulate and distribute air. Note: building codes require that the blades must be at least 7-feet above the floor. When dealing with higher ceilings, one-third the distance to the floor is a good guideline. For shorter ceilings, try using a hugger (close to ceiling) style. Most offer sloped ceiling adapters if required.
Blade Sizes
In most cases 50-inch to 56-inch blade spans are the best selection, a 36-inch to 46-inch span is best for small rooms (10′ x 10′). For extra large rooms, try using two of the smaller sizes for best air movement.
Lighting
A couple of years ago the US Department of Energy banned the use of medium base incandescent light sources in fans. Most light kits for fans are now offered in halogen or compact fluorescent. Some fans include a light kit and many offer covers if the light is not wanted; some fans require the light kit to be ordered separately.
Fan Controls
Every fan is different when it comes to the controls and the options offered, be sure to keep this in mind. Some fans only have pull chains (on/off) but most offer wall controls or wireless remotes (sometimes ordered separately). Wireless controllers require a receiver in the canopy of the fan (usually included with the controller). Most fans can be reversed, some have to be done manually and some can be done with the controller. Be sure if you are adding a light kit to check that the controller includes separate switching for the light. Not every controller will work with every fan, so double check the compatibility.
Energy Information
Fan manufacturers are required to provide the energy information such as watts used, cubic feet of air moved per minute (CFM) and total wattage of the light kit. Many offer eco fans that carry Energy Star labels or have the new DC motors (which are about 75% more energy efficient than AC motors).