Make a list of e-zines that rated 4 or 5 on content, and 4 or 5 on advertising environment. There won't be very many of them. Let the publisher know that you like their work, and you're interested in advertising. The Vital Stats Ask for their current circulation, frequency of publication, current ad rates, terms and specials. A lot of publishers will offer a free classified ad, even if they don't do subscriber ads.
Record responses as they come in.
Send a second inquiry to anyone who hasn't answered after one week. If you still don't get an answer, don't advertise with them. Rating The Best Prospects For e-zines with equally high ratings on content and advertising environment, you want to start your campaign with those that have the lowest cost to reach your target audience. If they offer you a free ad of any kind, you'll of course want to take advantage of that, although you shouldn't expect great results from a free ad. E-zine readers in other fields will typically be more tolerant on content quality, and much less tolerant of a lot of ads.