Beijing quite safe as long as you are out in the open, CCTV cameras everywhere. Sometimes petty theft (crowded areas). No problem wondering around in the middle of the night.
Be aware of ladies around the tourist spots (when you're alone) asking you to join them for a cup of tea to practice their English (scam) or inviting you to buy their art paintings (prints
). Don't give your camera to a 'local' around the tourist spots offering to take a picture of you and your wife. When buying stuff try to give the exact amount as fake money is EVERYWHERE (taxis are quite famous for this and always take one that have a working meter). ONLY use green and yellow striped or blue and yellow striped taxis (most taxi drivers only speak mandarin). Bargaining is very common except in grocery and higher rated shops. Should you visit a local silk market, bargain heavily, they might start on 800RMB for a shirt, bargain 80-90% less. Rather skip branded clothing... And for photography
you can take a walk (or taxi) to CCTV building and China World Trade Center, quite safe (you might be approached by one or two ladies on the street for a 'massage' though). Can also visit The Place, with it's 250m long LCD screen starting up at 8:00pm, short films every half hour.