If you are in business, you have developed areas of expertise that other people are interested in. For example, you know how to differentiate your product or service from your competitors--why what you are offering is superior and worthy of consideration. That becomes the basis for a checklist of what should be considered before making a purchase, and that type of information is valuable to others.
If you have been in business for a while you may have several areas of expertise that you can share and many options for getting the word out. An informational brochure and a periodic newsletter are two commonly used and relatively inexpensive methods. Others are writing a column for a local newspaper or sending a post card as part of a direct mail marketing campaign. A more ambitious method is to hold a seminar or demonstration on an informational topic or offer a presentation as a public speaker for community groups. Writing a blog is a new and increasingly popular method.
For subject matter, use topics that help your target audience with their problems.