We always go down around the Pawleys Island area. It's about 20-30 minutes south of Myrtle Beach, so you miss out on alot of traffic and more expensive housing, but it's still close enough that you can get there for all of the attractions. It depends on what you want though.... if you want to be amongst the crowd, then stay in Myrtle by all means.
Now that I think of it, I did stay in Myrtle Beach once. As a track team, we went there for spring break 2003. We got a hotel right on the beach. It was awesome. Wake up and open the blinds...... hello Atlantic Ocean! Of course, then it was too cold to swim in the ocean, but there were 2 pools in the hotel.
As for what to do, if you like fishing, get a charter out on the ocean for some deep-sea fishing. They have various distance/time trips to cater to what you want. As long as you don't get seasick, it's a great time and you can catch some BIG fish