While you never know how long it will take you to get to your destination in a taxi, it is nice to take the subway, which is reliable. While the subway does not cover the entire city, if it goes where you want to go, it is worth trying. Especially at rush hour, it beats getting on the road and can be much faster than a taxi.
The Beijing Subway system does connect some of the major tourist destinations such as Tiananmen Square/Forbidden City, Wangfujing, the Lama Temple, the airport, the train station and the Olympic Park.
If paying cash it costs RMB 2 per ride, but if you use it regularly buy some extra tickets or get a prepaid swipe card. For a swipe card you pay RMB 20 deposit, refundable, plus whatever amount you want to put on the card. Sometimes the lines at rush hour to buy tickets or update swipe cards can be very long, so best to get this sorted out. Also make sure you get in the right line, one is for swipe cards, the other for RMB 2 single use tickets. Look in the window at what people are doing then get in the correct line.
Swipe cards can also be used on buses.
Paper ticket single use.
The two original lines are "1" which goes east-west across the city and "2" which is a loop line following the second ring road. New lines include "13" which runs across the top of the city, line "5" which is north-south and goes close to the Olympic Green. Also new is the airport line and lines "8" and "10" which service the Olympic Green and northeast side of the city, including the east third ring road.
We presume the missing lines (3, 4, 6, 7, 9, 11 and 12) will show up at some point!
Signs on either side of the tracks tell you the upcoming stations, so have a look to see which side you need to join the train on. You might want to count your stops so you know when to get off.
Announcements are in Chinese and English, but not always easy to hear.
The Beijing Subway viewed at street level.
Most maps & guidebooks will show you the subway line. Ask your hotel how far to the nearest one. Get them to write the name of it down in Chinese. Then on the street you can ask people to point you in that direction.
You should learn to ask "Subway station at where?" :
If you have the English/Chinese "Beijing Tourist Map" stations are cryptically marked with a red circled "D" standing for "Ditie Zhan" (subway station).
Signs show which side of the platform you should board on and allow you to calculate how many stops you need to go. It also shows travel time to stations. The greyed stops are behind you and to go there you'd board on the opposite side of the platform.
The red and blue circular arrows show the interchange stops.