Wood burning fireplaces build up creosote and soot on chimney walls very quickly. These materials are extremely flammable and thus the chimney should be cleaned regularly. You should also inspect your chimney cap that is open on the sides with mesh to protect birds and debris from entering the stack. Make sure the mesh is intact and the cap side are open and clear of debris so smoke and head can safely exit.
Many people will hire a professional to do this task as it requires getting up on your roof. The basic tools are a chimney brush that matches the diameter of your chimney, and associated extension rods depending on the vertical length of your chimney.
Once safely on the roof, remove the chimney cap and scrape off the creosote with a wire brush. Then insert your chimney brush down the chimney scrubbing the edges. Inside the home, you’ll want to attach a plastic bag to on opening to catch all the debris.
Here is a sample video from Wrought Iron Dude