when in Rome, do as Romans do

When in Rome, do as Romans do is a very common cliched term you most likely have heard at least once in your life. What it means is that under certain circumstances, you should abide by the customs of that society or group if you are a visitor there. It is usually a way of saying you should be polite and also advantageous, but the phrase can also be used simply to say when you are in a new place, you should try new things.