When we drive, we base our motel choice on a couple of things. First of all, we never book in advance because we can never be sure exactly how far we'll get before we want to stop.
When we get into SC, we stop at the visitors center and get the coupon book for the hotel specials. Then when its getting to be about time to stop, we start watching the billboards to see what's coming up. We use I-95 so I'm not familiar with I-77, but at least on 95 there are 3 or 4 motels at virtually every exit. We just find the one with the best rate and stop there for the nite.
Steve