If you have stained glass doors from creosote deposits, allow the glass to cool down then wipe it on the inside to get rid of the loose debris. Ideally, use damp newspaper for this. If the deposits are tar-like and sticky, you should light a hot fire and burn dry, seasoned wood on it for several hours. This should effectively burn off most of the deposits.
You can buy a special glass cleaner from many of our retailers and this is great for removing deposits. Another lesser known cleaning technique is to dip a damp wad of newspaper into the ashes of the wood then rub it vigorously on the glass to remove stubborn deposits. Then, use a fresh piece of damp newspaper to wipe down the glass again.
Finally, to help prevent creosote from building up on your glass doors in the first place, burn your fire with the air control open. This keeps the smoke away from the surface, making it harder for deposits to form.