Littlemo, at a minimum, get one of those 3 prong testers with the lights on it like the others have posted photos of. Any hardware or big box store will have it. When you plug into the pedestal, plug that tester to an outlet inside your RV and see if the lights show correct wiring. Best advise is to buy one of those Progressive Industries EMS boxes; you plug that into the pedestal first then plug your RV into the EMS. A good on runs around $200-250 but can save all the electrical wiring and devices in your RV as well as alert you to any ground problems. I have a 30 amp EMS for my rig.