It is a classic example of "rule by law" which is in full effect in PRC. You're required to register within 24 hours at the "police station", no details of the said station, no opening hours or any further information is given. The process is quite slow, the queues are long, and the officials are visibly irritated every time you come and wake them up from their slumber. Then there are people flying 3-4 times per week…
If you are staying in a hotel, you don't need to go to a police station. Otherwise, the person you are staying with should be able to help you find it.
> The process is quite slow, the queues are long, and the officials are visibly irritated every time you come and wake them up from their slumber.
Not my experience, but maybe I just got lucky.
> Then there are people flying 3-4 times per week to Hong Kong or Seoul on business, technically they are required to register every single time they enter China.
Those people presumably have some kind of permanent residence. It would be news to me if that required re-registration after each re-entry.