Depends on more than one factor
The best rate isn't necessarily where you think it'll be. Sometimes chains can be cheaper than Mom & Pop, sometimes not. Some chains like Motel 6 offer basic rooms for reasonnable prices (usually between 30-45$) but you don't get any breakfast with that. Other chains like 1st Inn, Budget Host Inn, Super 8 tend to be cheaper.
Visitors Centres on the side of interstate have free hotel discount coupon booklets you could grab to see if there's anything up your alley. Sometimes there are excellent deals in there but sometimes it just happens that you're in town during a local or national holiday or special event and all motels jack up their prices. Some States have higher taxes than others like Texas. Also, motels located in bigger cities will often add a 2-5% tax to their prices.
Having a AAA membership will give you a 10% rebate in certain hotels or if you are a Government employee, a senior, a military try to get an extra rebate. You can try to bargain at some hotels but don't be too pushy. Hostelling might be an option or look for the local YMCA in metropolitan areas.
Good luck!
Gen
Don't forget internet reservations
Some chains give a good discount for making your reservations via the internet. Even though I have a AAA membership, there are times when the discount for reserving on the internet is cheaper than the AAA discount.
You can use internet in many hotels, campgrounds, or search out libraries if you don't have your own way to access the web.
I don't like to be tied into reservations, so I'll tend you what I'll sometimes do. But you need a very trustworthy family/friend who you can leave your credit card number with to make this work.
If I'm on the road and realize that I might want to stop soon in a certain area ahead, I'll pull over and do a quick look in my AAA guidebook to see what's there. If there's a a place that offers the AAA discount, I'll call them to see if they have a room available. I will also ask them if internet reservations are cheaper. Sometimes they'll tell me, sometimes not. If internet reservations are their cheapest rates, I'll ask if they can waive doing that and consider my phone call an internet reservation. Sometimes they do. I guess it depends on how many vacancies they have and how anxious they are to fill a room. If they can't or won't, I'll call home and have my person who has promised to do this, make the internet reservation for me and then they call me back with the confirmation number.
I also know from experience that Motel 6 is almost always cheapest via internet reservations so, in that case, I usually skip calling the hotel. My experience also shows that they will virtually never let me get the internet rate via phone. So then I'll just call my person at home and they'll call me back with the confirmation number.
