wiring a 30 Amp Power Outlet 30A Circuit Breaker {{UPDATE}}

As they said green goes to the lug that is mounted to the box. If you want to go one step further use an ohm meter or a continuity test light to check from the neutral lug to the box itself. There should be NO connection or continuity from neutral to the box. If you were to check that after its wired it would appear that there IS continuity because the neutral and ground ARE bonded (connected) at the source (main panel).