I have a friend who works in the hotel industry, and he shared some insider tips with me!

1. A man and a woman go to check into a room, the one who arrives first checks in, and the other follows later; the front desk acts as if they didn't see anything. Don't ask at the front desk what to do if you forget your ID card, and don't ask if it's okay to register for only one person. (Because the answer is no.)
2. Usually, at budget and mid-range chain hotels, no one checks when you go for breakfast, because the hotel staff have fewer rooms to clean and generally no dedicated staff for breakfast. So, you can book a room without breakfast, then blend in with the crowd and go eat openly. But this doesn't work at high-end chain hotels.
3. If you leave the hotel for more than 30 days, Uncle Hat will come looking for you, asking you to recall what happened at the hotel. You must honestly tell the truth, as surveillance footage is usually stored for about 15 days (up to 30 days at most).
This describes the general situation, suitable for most hotels.