Ensure that the cartridge type and shot size is suitable for both your purpose and your gun. If you use non toxic shot make sure your gun and cartridge are compatible, otherwise damage could occur.
Never imagine that a heavy load and a tight choke justify shots at extreme range.
Do not allow cartridges of different bores to become mixed. A smaller size (sat a 20 bore) can be inadvertently loaded into a 12 bore gun and lodge in the barrel. If a 12 bore cartridge is then loaded and fired, it can burst the barrel. In the case of a misfire, keep the barrels pointed in a safe direction and open the gun cautiously, after waiting 30 seconds.