Select the fan for its function before you do anything. An enormous fan is hardly necessary for a small bedroom, while a very cool-looking small fan is not going to be of much help for a family room with a cathedral ceiling.
Be aware of the size of the room when sizing up the fan blades. Most fan manufacturers include a scale for fan blades based on square footage. Fan blades are measured by diameter. Recommended maximum blade sizes are 36 inches for a room that is 100 square feet; 42 inches for 144 square feet; 48 inches for 225 square feet; and 52 inches for 400 square feet.
Consider the height of the room and the height of the inhabitants of the house when choosing a ceiling fan with a light fixture. Light fixtures can add another half foot or more to the overall size of a ceiling. If those living in the house are tall, take into consideration the potential for hitting one's head on the light fixture if the ceiling fan is hanging from a 10-foot ceiling.
Take note of the traffic in your home when choosing a ceiling fan size. If the ceiling fan is situated over a table or a little-used room, a ceiling fan with an extravagant chandelier is less likely to present problems. When choosing a ceiling fan situated in a part of the house where this heavy traffic, such as the middle of a living room between the kitchen and the entryway to the bedrooms, you should probably go wtih a smaller fan without a light fixture to avoid accidents.