ACA maps are great if you want to only follow their routes. On my cross country trip, we used them until we were sick of Kentucky and wanted to duck out earlier. From then, we used Google Maps whenever we were at a wifi spot to plan out our routes.

Every state we checked for paper bike maps, and whenever they had them we really enjoyed them. Kansas, Oregon, Colorado to name a few great states with maps that detailed shoulder size and how much traffic there was daily.

Another big thing is just talking to people left and right. Talking to people is half the fun for me, and locals can know some good stuff about their roads. Learned about some awesome detours, beautiful backroads, and where NOT to go, thanks to many many people. All in all, I'd recommend staying open to any information, even while on the trip itself.