Lanzhou, a long strip of a city, is divided into two basic sections: the eastern and western ends of town. There is no special area that you should want to chose, although most of the hotels are situated in the eastern end. The food sections of town are scattered about, as are the city sights. If you are looking to quickly move on, to Xiahe say, or to the north, then being near to the transport routes would obviously be useful. If local sights are your main interest then a hotel with access to the two famous caves, the Bingling Si Caves and the Maijishan Grottoes are to be considered.
For those after the best, both the Friendship Hotel and the Haitian Hotel provide comfortable lodging at a reasonable price.