Hello Jeff, and welcome to TN.
You don't say what kind of detector you have and that would make a difference, if it is water proof or not, if it reacts to heavy salt mineralization. It's like saying, "I'm going fishing, where should I go?" We need to know what your got to work with in order to help you much.
Generally you would look at the beach and see where people are sitting, laying down and playing and check those areas. If it is water proof, move into the water and look for cuts and holes where it drops off suddenly. Remember drops in high tides are in different locations then low tide, but most drops end up being moved with the surf and tides. Always check cuts and holes in the beach, especially where rip currents may have worked on the beaches.
Always check the beach access paths, paths to bathrooms, showers, anything like that. I found a nice diamond ring not 4 feet from wooden stairs leading off the beach the last 5 secs of a hunt. If I had stop hunting I would not have found it.
Check this link out and read all it has for Beach and water hunting.
http://thegoldenolde.com/
Good luck and good hunting