There is a certain etiquette to maintain inside of a public steam room. First and foremost, you should clean yourself and make sure your body doesn’t smell. This is especially important if using a steam room after a workout to help recover muscles. Second of all, you should sit on a towel, whether you a already wearing one or are in a bathing suit.
While it is OK to chat with other users of a steam room, you should note that if someone has their eyes closed, they probably don’t want to engage.
The most important rule inside of a steam room, though, is to not mess with the thermostat if someone is already inside. If you would like to lower or increase the temperature, make sure that everyone already inside are OK with it first.