If you have an existing wood fireplace you may be looking for a gas or wood insert. Bring all dimensions of the fireplace cavity (width x height x depth) along with the depth of the lintel (the thickness of the material that crosses above the fireplace opening). Also bring photos of the fireplace inside and outside of the building.
If you do not have an existing fireplace then you may be looking for a free-standing stove. For wood stoves, measure the diameter of the wall thimble (opening into the chimney) and bring a picture of the outside chimney.
If you are looking for a freestanding gas stove, bring a picture of the preferred location along with one of that location from the outside of the house.
If you are interested in a factory-built wood burning fireplace to be built into a wall. Bring a photo of the wall where you intend to have the fireplace installed along with a photo of the outside where the venting will be located. A picture of the roof above this location would also be useful.
If you want it to heat, how large is the room (width, length and height) it is to be installed into.
Will the fireplace be installed in the basement, main or second floor.
Is the fireplace to be located flat on the wall or in a corner and will it sit at floor level or do you want a raised hearth.
For gas fireplaces stoves or inserts determined the nearest location of the gas supply in your home and the distance to the new fireplace.
Have as many photos of your home available to convey your ideas along with pictures from magazines of fireplaces you like.