Newbies finding diesel fuel

Wow, can't say I've ever given much if any thought about where to get fuel next with the exception of non E or race gas for my sleds or the first trip up the Alcan highway, and even that trip I just carried 5 gal just in case and called it good.
To the OP, if pulling into fuel stations is intimidating you then you need some more practice with that big camper, IMO. Or get a slip tank or Titan or Transferflow tank so you don't have to re-fuel with the 5ver attached. You could get a used slip tank with pump for a few hundred $ and carry 40-80 extra gallons.

The gas buddy app for android phone is a nice app but it doesn't show always that the station selling diesel is accessible without major headaches. (Way too many stations have the fuel lanes perpendicular to the road and if cars are parked in front of the station, it is almost impossible to get enough clearance to make the turn. Angled fuel lanes work much better.) We use it tho in conjunction with Fuel Book 3.0 (free app for android phones). Fuel Book lists truck stops only. You can generally get a picture of the station showing you the lay out. Someone mentioned using truck lanes and that is great advise everywhere but Indiana. In Indiana, the truck lanes are restricted to OTR truckers because of the way they do their fuel tax. That being said, they also have lanes marked auto diesel that works for RV use.

Got a Next Exit Guide and it is a PIA and have given up on it.

Ipad and IPhone both have a APP that shows truck stops, how far the next one is, the services they provide, and etc and I think mine was 2 bucks and well worth it. Mine is call "All Stay Truck & Travel"

In all the miles I have travelled over the Western US and Canada during the last 6 or 7 years I have never had a problem finding Diesel.I agree that truck stops and travel plazas are nice, but most of my travels are away from the main highways and I have never come across a station that I could not use. Finding fuel and accessibility of pumps is not something I ever worry about.

my fuel stops usely are the same as coffee stops so trck stops

I haven't run out of diesel crisscrossing the country yet and we do avoid interstates when possible. There are many fueling stations on US highways where local truckers fill up. Most of them have separate diesel pumps away from the auto pumps and plenty of room for MH's or fifthwheels.

I have friends with fivers who make a "top off the tank" fuel run with the tow vehicle while the RV is in the CG or RV park. They say this helps reduce the number of times they have to find a place they'll fit into all hooked up. Actually more of a problem with gas tow vehicles, because those nice big truck lanes are diesel only. Easier to a diesel pump with big rig room than a gas pump with enough space.

Gas Buddy app for smart phones works great too.

I can't believe no one else has suggested this, get a Next Exit Guide, at Camping World or Amazon.com. It covers every major highway in the US and tells you exactly what is off every exit, fuel, hotels, restaurants, wal marts, etc. I'm sure there is an app for that but it's much easier to me to have a book that I can look at and decide how many miles before a gas station comes up. The nice thing is that businesses that are rv friendly (big enough to drive in & out of) are in RED. We have traveled with one for years and they are amazingly accurate. We are in the group of rv'rs that avoid Flying J like the plague, they are almost always hard to get in & out of, such as a 90 degree turn and try to get out of the parking lot without someone backing into you. I've said many times before who designed Flying J's rv islands??? Fuel, a dump and propane all crowded together, dumb, dumb, dumb.