It could be as simple as a box with a broken rule. Readers can sign and fax or mail it back to you for a free subscription. Either way, reader responses build a database of potential customers who've expressed interest in the company. If you're starting your first issue, devote a column to introducing your newsletter and telling readers its mission and frequency. Include background on your own credentials and your business services.
Some newsletters carry mastheads, others just a return address.
Research your subject first. Find out what's his or her most important message to communicate to clients. When I interviewed Rupert Murdoch, I got the essence of the entire story by asking this open-ended question. Stick to them. If you're the coordinator as well as the writer, work out a budget and a production schedule.