There are approx. 70,000 taxis going around in Beijing, most of them are Sonata, Jetta and the red flag. Because of the Population of Beijing is Huge, at peak hours, you will find it a bit difficult to hail a taxi on the streets.
Because of the Olympic, Most of the taxi drivers can speak more or less English now, but you are still advised to write down the name of your hotel or destination in Chinese. So you are able to show it to a driver.
All legitimate taxis in Beijing charge by using meters, so you can just get in the taxi and pay when you are getting out. By the way, I suggest you to take fapiao (receipts) which willl be printed automatically for you.
Taxi rates(all charged by RMB):
In the daytime price = starting fare 10 (first 3 kilometers) plus 2 for every succeeding km within 15 km and 3 for every succeeding km after 10 km.
In the Night (from daily 23:00 to the next 05:00 ) price = starting fare 11 plus 2.4 for every succeeding km within 15 km and 3.4 for every succeeding km after 10 km .
Waiting in a traffic jam or for the lights to turn green, it is charged as 1 kilometer per 5 minutes.