One of marketing’s basic rules is to know your target market well. Know their interests and things about which they like to be kept informed. If you come across information that you feel would be useful to your target audience, add it to your ezine (crediting the author or source, of course). The more useful the information you provide, the more likely your readers are to stay subscribed.
For lots of advice and free tips, check out the FREEBIES page at the VA Success Group