These instructions are for disassembling a hammerless, side-by-side double barrel shotgun. Whether old or new, most shotguns of this type share very similar mechanisms, and the disassembly procedure is generally the same regardless of make, model or gauge.
Make sure the safety is on. This is usually a small switch located on top of the gun just behind the top lever. Generally, the on position is with the switch slid back toward the rear of the stock. On many models, the letter "S" will be visible when the safety is set. Verify this, however, in the documentation for your specific gun, or consult an expert if needed.
Check that the gun is unloaded. To do this, hold the forearm with one hand and use the thumb of your other hand to press the "top lever," located behind the barrels. It should move freely to the right side.
The barrels will then pivot downward, away from the stock. This will expose the extractor, and the back ends of both barrels. If the gun is unloaded, you should have an unobstructed view through both barrels. If the gun is loaded, you will see the back ends of the shell casings in each barrel. In this case, pull the shells out of the barrels using your fingers. Once you are certain that the gun is unloaded, close the gun back the way it was. You should hear an audible click, and the top lever will snap back into place.
Always be cautious when working with firearms. If the procedure is unclear to you, consult someone with experience before proceeding.