There is no technical problem a computer can throw at you that will be worse than the personalities that a human could throw at you. As a web design business owner, you will have to learn how to deal with every type of web design client in order to have a successful business.
Keep in mind that if your web design clients knew what they wanted, they would design their websites themselves. Even if they sound completely sure of themselves from the beginning of their website to the end, remember that you are still the professional. If you do not inject your professional opinion into the design, you will invariably face a great deal of rejection and unneeded revisions.
Do not do work for anyone other than the decision-maker of the project. Also, put a limit on the number of revisions that you will do for a client. Third, write down the descriptions that people give you over the phone so that you can play it back for them when they decide that you have not given them exactly what they wanted (and you did).