The National Fire Protection Association recommends that chimneys be swept at least once a year at the beginning of the winter to remove soot and debris. Find a certified sweep in your area via the Chimney Safety Institute of America.
In addition to cleaning, a chimney sweep should inspect the chimney structure for cracks, loose bricks, or missing mortar. Chimney liners should also be checked for cracking or deterioration.
A cap fitted with wire-mesh sides covers the top of the chimney and keeps rain, birds, squirrels, and debris from entering. Replace or repair a cap that's missing or damaged.
Choose dense wood, such as oak, that's been split and stored in a high and dry place for at least six months. Green wood and resinous softwoods like pine produce more creosote, a flammable by-product of combustion that can build up in the chimney.
Small fires generate less smoke, thus less creosote buildup. Also, a fire that's too large or too hot can crack the chimney.
Place logs at the rear of the fireplace on a metal grate. Use kindling, rather than flammable liquids, to start the fire.
Prevent errant embers from shooting out of the firebox with a mesh metal screen or glass fireplace doors. A guard in front of an open flame is especially important when the room is unoccupied.