Tests of faith
Traditionally, fung shui masters were considered men of wisdom and, therefore, were almost never questioned, while any recommendations they made were followed to the letter. In this day and age, individuals who dispense advice need to explain and justify their proposals to clients.
The client has the right to ask a consultant which school of fung shui he is applying (such as Eight Mansions, Flying Stars, etc), whom he studied under and whether some of his suggestions could be modified to suit specific needs. If a fung shui master recommends that you place a bamboo plant in a certain sector, for instance, it is perfectly acceptable to ask him why that must be done and what results it might bring. Fung shui masters who are evasive when responding to queries or simply state that that's 'just the way it is' are not to be trusted.
Furthermore, real fung shui masters know better than to give free advice when it's not called for. If a cousin's friend visits your home and points out a fung shui flaw that has been gleaned from a book, it is best to ignore them.