I've been doing this for a lot of years but a couple of weeks ago I made two newbie mistakes on the same weekend.
1-Got all hooked up and couldn't get hot water. Result, make sure you switch the winterizing valves back before you burn up the heating element. Yep, I did.
2-For a while the water was off at our campground so I was just going to use the pump. It never would prime and start pumping. Result, make sure you open the valve to the tank if you want to get water out.
So, for your own sanity don't make the mistakes I did.
2016 Keystone Laredo 297SRE
Andersen Ultimate
2002 Chev. 2500HD Duramax/Allison/4x4