Hi there,
if you require a local sim card (be aware usually you can't receive sms from abroad, but send to phones abroad). I believe the best is to get them before leaving the airport, more specific before or while you wait for your luggage.
At the same place it is told to be the best place to pick up a FREE map of Beijing, which has both chinese and english on it. Two weeks ago I couldn't find one, but maybe they have them again - so if one could bring me one I would be most deligthed (its really usefull for taking the taxi).
I can give you the GPS coordinates of some sigths, so if you want to bring a device, you can navigate easier.
Have fun and see you soon....
jab