It is very important to familiarize yourself with the basic operation instructions of a propane tank before you attempt to use it on your home grill. This is because misuse of a propane tank or gas valves can be very dangerous. The pressure relief valve on the propane tank can be handled only by professionals, but the valve on your grill can be reset by you, since it doesn't require certification or tie into the safety and actual functions of the tank, as the pressure relief valve does. Resetting the valve helps aid the grill's performance and drain residual gas from the lines.
Turn off the propane tank and disconnect it from the grill.
Switch the gas valves on the grill to the highest possible setting. Wait several minutes. While the valves reset, the built-up pressure will be released.
Put the gas valves on the grill to the "off" setting and turn off everything on the grill.
Connect the propane tank back to the grill and switch the tank valve to the "on" setting. As you turn the knob, do so as slowly as possible so as to not build up too much pressure too quickly.