An organized writer walks his client through the process of creating a new composition, whether it's a book, article, business plan, or a slogan. This will lead to fewer revisions and a lot more happier people.
Business owners live in a world of distraction. Even the ones that don't pick up their cell phones every five minutes certainly have a million thoughts going through their heads at any given moment. It's up to the business writer to wade through it all, keeping on task until all the information is collected.
Journalism Questions Always Helpful
No matter what the project, it's appropriate to ask questions starting with who, what, where, when, why, and how. Even when they seem unlikely they can bring out some important aspect of the product brochure or business card to be written. This can be an excellent starting point for a writing system.
Over time, a writer gets a sense of what type of questions will get him the answers he needs. Maybe it isn't even questions for you - maybe you have a list of words that are helpful memory triggers, or a checklist of some sort. The purpose of the writing system is to draw out as much information as possible from the client the first time you speak, minimizing revisions.
One final thought on writing systems: even if you make a very slick looking form to keep track of the information, don't just have your client fill it in. You're the writer - that's your job.