I was a kid in the 60's, so I grew up with cars that only had an AM radio. It had five pushbuttons for your favorite stations. I don't remember 8-tracks before about 1970, so you were pretty much stuck with the local stations except after dark when certain stations would carry for hundreds of miles.
Self-service gas stations didn't really get popular until the 1973 Oil Crisis. Even then, it was pretty common for gas stations to have both a self-service and full-service options especially for the major chains. As mentioned, many chains had their own maps. I'd pick up the maps everywhere we went and would see how the proposed highways became under construction and then completed. This started to change with the freeway revolts in cities circa 1970. It can be fun to see what might have been (and depending on your POV, what was lost).
The interstate system wasn't complete, so you'd be riding happily along and suddenly hit a two lane section or be steered into a town. This was especially common out west. Glenn Frey was standing on a corner in Winslow AZ because I-40 had yet to bypass the town. That US 66 big bend in Arizona that was romanticized in "Cars" was actually a royal pain, especially for my dad as we were hauling a pop-up camper. Along with the hotel chain books, there was also a national campground directory though it's accuracy left something to be desired. And finding some of the campgrounds was an adventure in itself as they were often off the beaten path.
A lot of major roads would also get backed up. You could be stuck at a rail crossing for 30 minutes with a train building its manifest at a switchyard that was inconveniently next to the main drag. Or stuck at a drawbridge on the main drag. You don't see too many drawbridges on major routes anymore like the I-64 drawbridge in Chesapeake, VA.
A lot of roads had waysides, picnic areas which may or may not include a bathroom (which was frequently an outhouse). They still exist, but you don't see many of them. Especially the ones with outhouses. However, interstate rest stops have mostly gotten better, and with WalMarts and McDonald's almost everywhere it's pretty easy to find a semi-clean restroom these days.
Cable was pretty rare, so you only got the local stations in the hotels. This may mean not even getting the major three networks in some more rural areas, though sometimes there were repeater stations from larger cities. This is assuming your room had a TV. There were also some fun hotel quirks like the beds which vibrated for a quarter. There were also a lot of weird theme hotels (like wigwams) that are mostly long gone.
There were also towns where you wouldn't be welcome after sundown, especially if you were African-American or had long hair. This was true well into the 70's. You might even be warned to leave if you were an outsider if you were young and clean-cut. Especially if you looked Jewish.
Hitchhiking was far more common. It wasn't unusual to see a line of long-haired young people along the interstate or on a freeway ramp especially near the outskirts of any city. Ride-sharing was done mostly through college bulletin boards. I once got from SF to Milwaukee from a ride board listing in Berkeley.
Cars didn't have power steering. Drive a big old Oldsmobile or Chrysler from the early 60's sometime. It really is like driving a boat. You also didn't have power (much less anti-lock) brakes. The first time I experienced power windows I was amazed. They frequently didn't have AC, especially if purchased anywhere in the northern half of the US. I don't think my parents had AC in a car until the 70's.
That said, it was also interesting. Chains weren't nearly as ubiquitous along the interstates. It wasn't unusual to only have local restaurants to choose from. Despite what others said about traveler's checks, they weren't usually difficult to cash as long as you were buying something so they were frequently accepted at hotels and restaurants. (I used them through the late-70's and 80's with no problem.) Some of the worst chains are deservedly gone (e.g., Stuckey's). There were a lot more regional differences in food back then, even in the nomenclature. You might ask for barbeque only to get Sloppy Joes.
Finally, there was no such thing as a No Smoking section. People smoked everywhere. On TV. In the lobby of gas stations. Even on airplanes. I don't miss that at all.
