Go to
http://chabotgunclub.com/ and check the Range Commands link. These are pretty much the norm where there is a formal procedure. Public ranges are good examples.
At one other club in Richmond, CA we have a bay open on the weekend for holster/pistol practice. There are usually no more than a dozen shooters at a time so we just check with the shooters as to whether they are ready to tape targets and then announce that the range is cold. When we know everyone has taped/set up their targets and is behind the line we announce the range is hot.
There is a formal introduction for new shooters, but most of the shooters are competitors and little explanation/reminder is needed.