FIRST of all and IMHO more importantly is look at the "entrance driveway" BEFORE you pull in to see how steep it is.
I was shocked to find out how many have too steep an incline to even get in without dragging the hitch or bottom of a Class A or C.
First glance is if there are already a lot grooves in the pavement pass and find another station.
I know only get gas where there is also a truck stop. I know I can always enter there on a flat driveway and drive around to the gas pumps.
The pumps? Well you will acquire a new way of getting gas and that's always looking 'ahead' of just the pumps to make sure you have an exit way from the pumps to get out towing.