Hi All - my husband and I are currently planning a road trip for next year (Sept) for 8 weeks starting in New York and ending up in Vegas. We have looked at out route and will be taking in Myrtle Beach, Atlanta, Nashville, Gracelands, New Orleans, Houston, San Antonio, Dallas, Phoenix, San Diego, LA, San Francisco, Sacramento, Yosemite Park, and then Vegas. We have never done a road trip before and would appreciate any help. We have looked at our route and picked out some RV parks and campsites but should be book them in advance or can we just turn up. We are from the UK and are very excited about this trip but feel a bit anxious as we dont really know what we are doing 
Go, you! That will be an epic trip and I’m so glad you’re doing it and taking your time. What a blessing.
just one comment at the moment: in between Atlanta and Nashville lies a lesser-known gem: Chattanooga, Tennessee. We have lived here for a little over seven years and I love it. It’s really very beautiful and there is so much to do here. Also, if the Civil War interests you at all, this is the epicenter and there is much to learn. The Ridge we live on the slopeside of, called Missionary Ridge, is dotted all over with monuments and signage describing troops/commanders from North and South, battles, situations, strategy, etc. And those signs, in addition to cannons, monuments, and other things, can be found all over the greater Chattanooga area.
If you are hikers, river, or train lovers, Chattanooga has you covered there, too, in spades. Here are a couple of videos to check out:
just 20 minutes from my house are some of the most curious and wonderful rock formations. You can see and experience them commercially at a wonderful place called rock city (seerockcity dot com) or, a bit further away, for about $5 or $10 at a state park called Cloudland Canyon. Rock City is the only place in town I have a season pass for! I love it. And if you’re traveling with a dog, per chance, they allow dogs! Mine loves it, as far as I can tell. 
Also, I have lived in Texas, Washington DC, Massachusetts, Connecticut, and Ohio; so if I think of anything more I can contribute to your planning, I’ll check back. Feel free to ask questions, too. I love traveling both here and abroad, love learning about the people and places wherever I go, and I love road trips!