The age old debate - there's no right way and there's no wrong way. (just don't piss off the art buyer, art director, or photo editor). There's always advice and you can take it or leave it. At Heather Morton's blog, at A Photo Editor, and at Burns Auto Parts Consulting, they point out there are pros and cons to each marketing strategy no matter what.
Doesn't matter though as long as you keep marketing yourself to the appropriate people. Do your research and make sure your work is right for the audience you're trying to reach. Don't just rely on email promos - mail a promo or make a few calls.
My suggestions would be these (and again I am only one person, one art buyer - for each person out there you will hear all sorts of different advice) but this is what works for me:
1. Email promos - Keep it simple and small. If the email doesn't open automatically because the image is too large chances are I'm not going to wait for it too load (unfortunately with web being instantaneous I expect the email attachment to be as well.). Link the email image to your site. As far as tracking goes - touchy subject because it is a useful tool but use it wisely. If you're going to follow up with an art buyer, art director or photo editor keep it professional and simple - something like "I'm following up on the promo I sent a week ago" and not "I saw you visited my site"... it makes some people uneasy.
2. Mailed promos - Another keep it simple but sizeable. I'm not a big fan of the huge envelopes and posters. I personally love the clear plastic envelopes with the promo completely viewable (it's another one of those instantaneous reads for me). I also suggest looking into the paper you're printing the promo on and the printing process. You want your work represented in the best possible light and not on over saturated paper that the color looks dull. Also make sure to double check your mailing list and spell names correctly. I can't tell you how many promos (mailed and emailed alike) where my name has been spelled incorrectly and it's all over the map so I can't fault agency access or ad base.
3. Phone calls - Professional, not too sales-y and 5 minutes. If you're making calls definitely leave a message and if you don't get an immediate response give it at least a week before you follow up. I usually screen calls (don't we all?). I know it seems harsh but if I took every call I would not get any work done for my clients. I usually amass a bunch of messages and take Friday morning to do all my callbacks. If you don't leave a message but I see you're calling me everyday, it's going to weird me out a little. Keep the call short but comfortable. If I hire you for a job I want to know we can chat and you're not going to be too nervous, too pushy, etc. it's sometimes tough to get people on the phone but it's worth it to try and check in a few times a year.
4. Meetings - Try to get at least one meeting a year with your target audience. I love meetings and portfolio reviews, I really do. It gives me a great sense of the photographer or rep I am meeting with. Remember to bring new work and a fresh portfolio (not the same one you showed the year before).
But keep your name and your work out there - just make sure it's getting to the right people.