When hanging a ceiling fan, it is important to maintain safe headroom below the fan. Ceiling hugger or flush-mount styles should be chosen for rooms that have lower ceilings as the bottom of the fan should never be less than 7 feet from the floor.
If you are considering a fan in the bedroom, there is likely already a centrally-mounted overhead light. Although a central location is best for circulation, you may reconsider if the bed is directly beneath it and the ceilings are low.
If you want to swap an existing light fixture with a ceiling fan/light combination anywhere in your home, remember a CSA approved, Electrical Safety Authority mandated ceiling box and bracing system must be used to safely support the fan’s additional weight. Your existing light will not likely have this device— nor is it acceptable to attach the fan directly to ceiling lumber (as was acceptable in the past).