Many years ago, I was a student pilot and subscribed to Flying Magazine back when people bought printed magazines. Any way, they had a column called "I learned about flying from that..." In each issue, a pilot recalled a circumstance where they wound up in a tight spot and analyzed with hindsight clarity what they hopefully learned and what others might learn from their situation. Sometimes the problems were self inflicted, like a mistake or misjudgement the pilot made, but just as often it detailed a situation initially mostly beyond the pilot's control.
I thought it might be useful to start a thread here to detail some situations where we learned about RVing. So the guideline would be post about a situation that actually happened to you, how you dealt with it at the time, what you learned from it and hopefully how you would prevent it from happening again. Some obvious examples would be flat tire scenarios, induced sway situations, electrical damage from surges or mis-wired campground service, etc... Hopefully we will get responses from owners of all RV types.
I'll kick it off. I've been RVing pretty much my entire life. My family owned motorhomes when I was growing up and we traveled all over the country. As an adult, my family has owned three motorhomes and now, for the last 2 years, a travel trailer. So, while I was well educated on general RV maintenance and mechanical issues, I didn't have a lot of experience related to towing heavy trailers. I did a lot of research and picked up on most things pretty quickly settling into a comfortable setup routine. I became tired of waiting for the somewhat slow electric jack to reach the ground during setup and noticed that sometimes people used lynx levelers under the foot of the jack so they didn't have to lower the jack as far. Seemed like a reasonable idea, so I started doing it myself. Shaved a couple of minutes off setup and everyone was happy for several trips. Then one day, we set up on a slightly down hill campsite. Nothing too severe, but a gentle incline. I went through the same set up routine as had become the new "normal": back in, level side to side, chock the wheels, put out a stack of lynx levelers and lower the jack to raise and disengage the tongue. Only this time as the tongue disengaged the ball, the trailer began to roll, sliding the jack foot off of the stack of lynx levelers.
Physics!
What was different about this time than all the other times I had gotten away with it? The slight down hill combined with raising the front end provided just enough momentum set things in motion. Fortunately, It wasn't a significant down hill or a drop off and when the jack foot came to rest on solid ground combined with the lowered angle it came to a stop only rolling a foot or two. What about the chocks? Why didn't they stop it? Well, they were the cheap plastic chocks and they were on smooth asphalt or concrete, can't recall which. The plastic just slid along the surface, never biting in.
That was the last time I put the jack foot on anything but solid ground. I also take greater interest in the lay of the site when parking and disconnecting. Finally, I do a better job of chocking with better chocks. Hindsight is 20/20, I should have seen a couple of issues here. First, I should have been more aware of the slope. Second, I should have been more aware of the shortcomings of the chocks I was using. Finally, I should have seen the potential for even a small shift to cause a problem with falling off of or overturning my tower of levelers.
So lets hear from others what's your story that others might learn from without having to learn "the hard way..."?
My Dad's truck had one...my wife's grandfather's truck had one...and I've seen many others! Make sure that fifth wheel is locked in place before pulling out! 
Best to learn from someone else's mistakes rather than your own.
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