Whenever I am planning promotional material for my clients, I start by writing down exactly what it is they are trying to achieve. I then write down the headings Who, What, When, How and Why. Finally, I set about answering each of the questions as if they were being asked by a customer. The end result is the key information that needs to be put into any promotional material. A lot of material is full of long, flowing sentences filled with descriptive prose that, while pleasant enough to read, doesn't answer all the questions that a customer may have about the product.
If a customer can read through your promotional material and gather just about all of the information they need, your material has worked. The next step is to get the customer to buy the product, and if the material is right, this should only be a formality. If they have read your material and there are a lot of questions to be answered, it can often end up in the 'to do later' pile or, worse still, in the the 'too hard' wastebasket.
Remember that customer service focuses primarily on making the sales process easy and uncomplicated for your customers. Well-thought-out promotional material is a big step in the right direction.