Some fireplaces are not efficient at all--on the contrary, older fireplaces can actually draw heat out of a house and send it through the fireplace venting system, even with the flue closed. If there is not an effective, air-tight seal on the front of the fireplace, air will move back and forth, even when the fireplace is not being used. Install a fireplace with a tight-fitting glass door or a door designed to work as heat shield to increase your stove efficiency.
Inserts are metal fireboxes lifted on supports that you can install inside your hearth. In a normal wood fireplace, heat radiates in all directions when the wood burns: this means that much of the heat is lost through the stones or base of the fireplace. Fireplace inserts give space for air to move around all side, drawing in much more heat so that the fireplace works more efficiently.
Fan-based systems use some type of insert component, but add a fan device that circulates air around the fireplace. The more air is moved, the faster heat can travel through a room or through a house. Some fans start when the fire heats to a certain point, while others you can turn on or off yourself.
A fireplace with good firewood will always be more efficient than fireplaces that do not use wood properly. Seasoned hardwood is the best material for wood stoves. Seasoned wood has fully dried out and can burn more easily, while hardwood is dense and creates more heat in less space.