I'm a newbie myself and, although I haven't burned up my heating element, yet, I certainly have tried. I had the electric and gas on simultaneously during my initial outing. That didn't seem to do any damage, so I proceeded to a more serious screw-up by leaving the water heater on while my FF-189FDS was parked for two weeks. Luckily, I had shut off the gas and nothing serious happened (I think-I still have hot water). After that episode, I read the operating manual(bout time dontcha think) to see just what else I could screw-up. That's where I read that trips above 4,500 feet altitude requires a modification to the gas jetting. I paniced, but have been reassured by about a dozen of my fellow RV'ers on this forum and Good Sam that all will be well with no modifications.
All in all, the most important thing I've done to protect the water heater is to read the operating manual, and make a sticky note to turn the darn thing off when I'm not using it. That and MAKE SURE it's full of water when you turn it on.
Welcome aboard!!