Never answer your door in the middle of the night. If it's someone you know, they'll call you. If it's not, and it's harmless, they'll go away.
If someone says they need help, call the police. This is a scam used to push the door in and invade your home!
If you have elderly relatives or neighbors, talk to them about it. It may be very difficult for people of more civil generations past to resist helping someone.