LIKE ANYTHING ELSE, you hire a designer for their expertise and their insight. If your car didn't run, you wouldn't tell your mechanic how to fix it. Your mechanic knows the best way to make your car go. A good designer will help make your business "go," and if you are willing to trust in their expertise, they will likely lead your project in a direction that will benefit you. In most cases, your role in the process of working with a designer should be one of information delivery and oversight of the project.
If you, in fact, have a clear and strong understanding of how your brand should be implemented (logos, color pallets, typography, imagery, book design, layout, etc.…) then you are better off hiring a production person. You will save money and time. But, beware -- there really is more to design than intuition. A designer with years of experience will be able to apply the best practices to avoid common mistakes,and have valuable insight about how to effectively communicate your brand message.They will also have resources and experience to make the end product happen faster and, in many cases, more cost effectively than a less experienced designer.
A designer should be able to present you with unique and targeted solutions that you may never think of yourself, and that is where their value lies. You have to be open to these new ideas and be able to think conceptually while evaluating them and deciding on the best course of action. Remember, effective brands are unique brands. I have had clients tell me "I want to look like this company.” The problem with this approach is that no one is going to listen when you and your competitors speak with the same voice. Your uniqueness and presentation sets you apart.
Qualify the designer: Having a computer with graphics software does not make someone a designer, just like having a toolbox does not make someone a mechanic. There are many kinds of designers specializing in different areas.
Companies with multiple design needs (print, web, corporate identity) should not hire 3 different designers to complete their communications system. When not managed correctly, this almost always results in an inconsistent application and interpretation of brand, leaving prospective customers confused. If your company needs a range of materials you should have one firm dedicated to championing and managing your brand, you should really be looking at design shops that can manage all of your needs. Some freelance designers will also have all the skills and experience necessary to complete such a package of services, just make sure their portfolio reflects this.
The best to each of you and may your journey be enlightening, encouraging and educational!