Charleston is discussed extensively in this thread:
http://www.lthforum.com/bb/viewtopic.ph ... charleston
If you're driving between Charleston and Myrtle Beach, by all means, don't miss the simple but excellent See Wee Restaurant in Awendaw.
Myrtle Beach can be a bit of a challenge. By all means, avoid the all you can eat seafood buffets. They are one tick on the side of human consumption from cat food. That doesn't stop those who know don't know better from lining up at the trough for seafood that was flash fried in April, then dumped back in the fryer right before its arrival at the buffet in August.
Two notable places where I had good meals were Greg Norman's Australian Grill which served good grilled steaks (but nothing better than you'll get at Gibson's or Morton's here). The other was Umberto's at Barefoot Landing, a Pittsburgh style Italian serving huge , solid, portions of meat and pasta.