Mostly good advice you've gotten so far, except that last post. No disrespect intended to Edd505, but I don't think any Motorhome owner wants to break camp and go out just to fuel up the rig after they get to their destination. That would work OK if you have a towable RV, but if you are towing a vehicle behind a Motorhome like what is being discussed here, that doesn't really work well.
I've been camping with a Class A towing various vehicles (flat tow) for 10 years. I don't recall ever once having to unhitch when fueling up. You just, like others said, take your time, use google earth or whatever to make sure you have a way in and back out, avoid fueling up in large cities or areas where gas stations are tiny and don't provide room to maneuver. Plan your entrance/exit carefully, and don't be afraid to wait for a bit for a pump to open up that gives you the space you need. Many a time, I will pull into a gas station, find a place to park alongside a curb or whatever close to the pumps, and wait there for a pump on the end with more room to come open, and take that when it comes open.
Truck stops like Loves, T/A, and Flying J already mentioned typically have a good bit of room to maneuver, even at the gas pumps. I look for those.
Will and Cheryl
2021 Newmar Baystar 3014 on F53 (7.3 V8) Chassis ("Brook")
2018 Jeep Wrangler JK ("Wilbur")