A friend came to Dalian on business and stayed in a hotel. Do I need to go through any formalities with him?

Generally speaking, hotel check-in is to register a person's ID card (or valid certificate such as driver's license) in one room, so you only need to use your friend's ID card or your own ID card to check in. As for how many people live in the room at night, that's your own business.

But with the approaching of the Olympic Games, I don't know if it will be very strict. I mean, how many people live in a room, register their ID cards. So, you don't have to worry at all, just do it as usual!