Check to make sure the tank is within the current hydrostatic test dates. The next service date is marked on the neck of the tank. Make sure that this time has not passed.
Inspect the tank's valve for buildup of debris. Check to make sure the tank's o-ring is intact, with no abrasions or dents.
Check the cylinder's working pressure. This is marked on the neck of the tank. This is important to ensure that you do not overfill the cylinder.
Open the tank's valve and bleed off the remaining air. Shake the tank to listen for any water or debris inside. If none is detected, then continue with the filling procedure.
Attach the cylinder valve to the filling station hose valve. Close the bleed valve on the hose valve.
Set the gas compressor to the fill pressure of the tank. This will ensure that it stops filling when the tank reaches that pressure.
Open the tank valve and the filling hose valve to start filling the tank. Once the compressor stops, close all valves and disconnect the filling hose from the tank.