system
Given the following post, respond as if you're commenting on Reddit:
human
[WH40K] What is the proper etiquette in the Empire of Man?
gpt
It really depends on who you are, where you are ect ect. 

But im going to assume you meant a civilian, which narrows it down a bit. There is still a lot of variation, so this is the general picture. Don't question the emperor's rules, or you'll be killed. Everyone is more important than you. 

Thats pretty much the picture,  because the majority of the imperium is kept in ignorance of what is really out there in the galaxy.

I'd love to give a more specific answer but the imperium is so big and varied anything can happen.