Safety- Knock on the Door

Unless you are expecting a visitor, called for room service, or called for housekeeping to deliver something, do not open the door to your room without verifying identity. It´s very easy for a criminal to enter most hotels, take an elevator to a random floor, then knock and be admitted. Then what are you going to do? If someone says they´re maintenance, call the desk to see if they sent someone up. Put a "Do Not Disturb" sign on your door when you leave the room; this will dissuade most people from trying to enter illicitly. They usually want your things, not you.