Hotels will have "taxi cards" for you to keep with you to get back and they usually provide a little card with the major sights listed in Chinese as well. Be sure to pick a few up for your bag.
There are tourist maps available in the hotels and Beijing is easy to walk around too, although it is very big. The subway is very easy to navigate in Beijing. This is a good option during peak traffic hours and it's also much less expensive than an already inexpensive taxi.
