It’s very location dependent. I was at a charger yesterday in Cupertino, CA and there was a Tesla branded sign posted that said “please form queue starting here.”
No queue when I arrived so not an issue.
Other sites have their own protocols/norms and it mostly depends on the physical constraints of the location. If the site is completely full, it’s usually pretty easy to see if someone (or someones) are waiting and where to get in line. Be respectful and observant is really all it takes - I’ve never had a problem.