Don't miss the Pandas, Tianamen Square and the Forbidden City. Pick a clear day to go to the Great Wall and wear comfortable shoes! You also might want to stretch your hamstrings before climbing the wall. It's pretty steep in some places!
Also try Peking Duck. The Asians eat every part of the bird, but if you look like a tourist, they probably won't give you the feet, the head or the stomach to munch on. This is a good thing, I think. Speaking of poultry, check out Kentucky Fried Chicken anywhere in China. It's cheap and it's better in China than in the states! I think it's because they use range fed chicken. Yum, Yum...
Quick Tips:
Pick up a langauge guide called "Fingertip Chinese" It's compact, concise and very useful!
Best Way To Get Around:
Tip: Don't pay more than 120 yuan ( US) taxi ride from the airport to your 5 star hotel in Beijing. There are a lot of crooked taxi drivers just waiting to rip you off. Your best bet is to avoid drivers who approach you directly with laminated cards that list the fare from the airport to Beijing. Trust me it's a scam!