Gone are the days when it was okay to lump all your contacts into a database and be done with it. As a business, you really need to be smarter. Customer segmentation is about grouping your customers according to a criteria that makes their experience with you better. It might start with looking at your contact form on your website? Is it a smart form? Does it collect information that you can use to segment your contacts.
Does it ask for:
Product/ Service: what each customer gets
Size of customer
Lifecycle: prospect, new customer, longer term customer
This presentation by Joel Knight asks the sort of questions that as a small business you should be considering. (25 mins well spent)