Going to China for a week- suggestions on travel/ cheap tix?

Hi all–

I’m going to China only for one week and I really want to have a good time. The only thing that is a must see for me is the Great Wall, and maybe Shanghai. I will problably end up flying into Hong Kong because the fare is so much cheaper, unless someone knows where I can get a decent flight straight into Shanghai.

Does anyone have any experience with the trains? How are they? Any suggested routes froM Hong Kong to Bejing within a week? How are the beaches?

thanks in advance.