What is the safe way to fill a propane tank?

I run into three types of propane fill attendants. (Class A horizontal) One just connects to the valve and fills the tank. Another opens the bleed valve as they fill the tank until propane sputters out. The other kind first bleeds the tank then connects to it and fills it. Each kind says that their way is the only way that they have ever done it and they have never even heard of the other ways. Which person is right? Thanks.