Wangfujing Snack Street and Donghuámén Night Market are two places every self-proclaimed foodie should visit while in Beijing. It's definitely a sight to marvel.
Din Tai Fung is internationally acclaim and famous. The Xiao Long Bao chain has locations all over Asia, Australia, the United States, and the rest of the world.
Du Yichu is located on Qianmen Dajie (i.e., Qianmen St). Qianmen St is a pedestrian walkway with retail shops along the strip and a major tourist trap.
Xianlaoman is renowned around Beijing for providing quality dumplings and being cost effective. The little shop is known to get packed fairly fast due to the mentioned quality.
Huntun Hou (aka Wonton Hou) is a Chinese landmark operating before the 1950's in the Wangfujing District of Beijing. The little shop has slowly expanded his operations throughout the years.
Beijing is known for its Peking Duck and the Chinese pronunciation is literally Beijing Duck. Dadong and Quanjude are the main heavyweights in Beijing with the best Peking Duck.