Each building can be classified under a certain element: tall buildings belong to the Wood element; square and flat ones to the Earth element; etc. Thus always examine the surroundings of a certain building to see if it can generate wealth at the expense of other buildings. When the surrounding buildings are supporting the premises you are interested in, this is auspicious.
Do not choose an office situated at the end of a long corridor or in an isolated wing of a building (isolation means a lack of Qi; also, if someone becomes isolated, it will disturb their interaction with colleagues and clients). Also avoid an office which is located directly across from the main entrance.
In Classical Feng Shui, external factors are of the most importance.