What does "other rules should be in place" mean in this case?

Question

Children should know how to dial 911, and what to do in case of a fire,” he explains. “Other rules should be in place in case someone phones, or comes to the door. Children shouldn’t answer the door, and if someone calls, it’s wise to say that their mom or dad is in the shower or unavailable at the moment.”

Answer 1

In this statement, you're referring to a set of rules of the house. Every family has their own set of house rules. These rules can cover a wide range of things: chores, curfews, etc. There are also safety rules to make you safe and secure both in and out of the house. It makes sense to incorporate the rules the police suggest:
Inside Rules

Children should know their complete home address, telephone number including area code, and parents' first and last names.
If children are old enough to answer the telephone, they should be taught how to dial 911. Practice with the receiver button taped down.
Children should be taught not to reveal any personal information about themselves or their family (their name, address, school) over the phone or to a stranger without a parent's permission.
If children are home alone and answer the telephone, teach them to say that the parent cannot come to the phone right now and take a message, or ask the person to call again later.
Have a "code" worked out with your children if you don't want them to answer any telephone calls but yours when they are home alone.
Teach your children not to open the door until they know the identity of the person knocking. Then teach them to whom they are allowed to open the door to. Just because they know the person at the door does not mean they should open the door to them.
Children should be taught how to lock and unlock the doors in the home.

The following address also provides OUTSIDE RULES and BAD GUY rules

Answer 2

You should have set rules (with the child) for a given situation. They should know how AND WHEN to call 911; not just call whenever (like if a stranger comes to the door.