How to take care of your shot gun

Keep your shotgun cared for and clean, doing this serves two purposes. First, it will keep the gun in good condition, which means it will last longer and remain in proper working order. The second purpose is safety.
With a shotgun that has been properly cleaned and cared for, you will ensure that your gun is safe for handling and reduce the risks of accidents and injuries.

Tips

Assume That Any Gun, at Any Time, is Loaded.

When someone tells you a gun is not loaded do not believe it until you see it for yourself. If it means offending a friend by checking a gun after he's told you it's unloaded, then so be it. Better to be safe than sorry. Always make it a habit to check no matter what. This is a very important habit to get into.

Keep Your Finger off the Trigger.

Without realizing many people place their finger on the trigger of a gun they are simply carrying, looking down the sights of, etc. Please don't do it! Keep your finger outside the trigger guard until you are ready to shoot! After shooting, move it back out of the trigger guard.

Be Familiar With Your Gun.

You must take the time to learn about the operation and features of the firearm you are using. Take the time to learn this while you are not shooting, this is when you should be learning about grip, shooting positions, trigger control, etc. So by the time to you step up to the firing line, you should already know how to operate the gun you'll be shooting.

Don't Shoot at Hard Surfaces (Including Water).

Water might not seem like a hard surface, but its density makes it pretty dangerous. It has a tendency to allow bullets and shotgun shot to ricochet (glance off) and fly off in an unintended direction, which is not good for obvious reasons. Hard surfaces like metal, rocks, and hard wood can do this too, sometimes they can even send the projectile back to the shooter.

Don't Rely on a Safety Mechanism.

Many guns have a safety device to prevent the gun from firing. These are usually reliable, but not always! Some guns have even been known to fire when the safety is released, so remember safety mechanisms are often useful, but not always completely reliable. Use the safety, but don't rely on it! Always keep the gun pointed somewhere safe to avoid accidents.

Which cartridges to use for which shooting disciplines

There are literally hundreds of different cartridge makes and loads to chose from.