Always lots to see and do in Beijing. For the best food eat where the locals do. Use the subway where you can, taxi's more expensive here than in other parts of China. Beware of anybody offering you anything that sounds too good to be true - it probably is. Enjoy the culture in the usual famous places and you can expect some English, go off the beaten track to practice more Chinese. Don't believe everything you hear about the pollution, some days have amazing weather and clear skies.
Insider Tip:Talk to the locals - most love to speak with Waiguoren, and are very encouraging.