If the job does require something special, a person will want to do some research into various designers to see who is actually qualified to the work they desire. A person can easily check references for a designer before they make the decision to hire them or not. The best interior designers are able to accommodate just about any need their client has.
Once people are able to see examples of a designer's work, they are more likely to hire that designer, especially if they like what they see. There are a number of factors to consider before choosing a designer to hire. If a person has a specific need or has a certain look in mind they need to be able to communicate that to their designer. If they have a good relationship with the designer they hire they will most likely be satisfied with the results.