Take Bus No. 5, 8, 17, 20, 22, 48, 59, 66, 67, 69, 71, 82, 93, 120, 12 and get off at Qianmen Station. Then walk about 300 meters along the Qianmen Street to get there; Take Subway No. 2 and get off at Qianmen Station. Then exit from B or C.
If you go to Beijing and not eat Beijing Roast Duck, you will be regret. It's really a yum Chinese food. I eat it everytime I went to China. It's my favorate and I can't help but drool upon seeing those tasty food.