I like to use the Rand McNally Motor Carrier's Road Atlas as one of my planning tools, since I like to use the trunk and secondary highways more often than the Interstate System (which does not very well serve the middle of the country). This atlas identifies the highways designated to carry vehicles with the maximum standard weights, heights, widths and lengths.
This is essentially the same road atlas Rand McNally sells in supermarkets, except that it has the additional map markings and limits and clearance information for truckers.
However, my primary maps are the tourist road maps provided by each state to visitors at no cost, and I carry a second atlas. In the RV, it is campground atlas (Reader's Digest or National Geographic, don't remember which) and in the car a Michelin Road Atlas of North America. I like the Michelin because it is tiled all at the same scale, rather than organized as separate maps for each state.
For trips I pre-plan in some detail (used to do this a lot when my wife still lived, because she liked having a plan) I've used Streets and Trips and DeLorme's Topo, which includes their Street Atlas planning tools but has much more map information. Those require a Windows computer to be available.
More and more, to check things locally, I am using either Google Maps or Apple's Maps app, on iPhone or iPad. Mobile data connection required, but it also means fresh information, almost anywhere I've been in North America or Europe.