[TexasSP]

Personally 18" is plenty short enough for home defense. There is little advantage to a shorter barrel length.

A good flash light is a must for sure. Something that can be mounted on the gun is preferable. They make several flavors that you can operate easily with your left hand.

Do remember with a shotgun you do still have to aim. While you don't have to be as accurate not aiming will cause you to miss your target.

I am with the rest, getting woke up at night puts you at a strong disadvantage. Especially if you are a heavy sleeper like me. However, like linc said an alarm (don't worry about being connected to the police as most of the time they take more than 30 minutes to respond to alarm calls anyway) is integral. Also have your phone close. If you have a wife get her to hide and dial 911 and inform them you have an intruder in the house.

Make sure to discuss these things with your family so they know their part if something like this happens.

One other thing to have is on the master bedroom have a solid core door with a dead bolt. My parents always had this growing up and it will buy you time when desperately needed.