Mailers trump E-mail. I'm afraid most people, especially busy people, won't pay as much attention to unsolicited HTML messages hitting their mailboxes. Some of those messages might not even make it through their accounts' spam filters.
Direct mail, OTOH, whilst it may still end up lining a bird's cage, has more of an impact on people. Not only do they have to spend some seconds opening it, but the mere fact that you spent money designing and printing a mail piece seeps into their subconscious and makes you appear if not more professional, at least more serious in your business. Anyone can send an E-mail message and it barely costs anything; a direct mail piece, that's different.
As abbypanda said, I'd target my mailings to the audience I want to reach. Make a list of addressees, print labels and send the pieces.
I just had ~200 flyers printed. One-sided, full colour; folded like a triptych, with the printed side inwards, so as to facilitate the sticking of the label and, more importantly, to make people open them. Since your mailing is a hook whose sole purpose is to establish first contact, I wouldn't spill the whole beans on it; you don't have enough room for that on an average 8.5/11" sheet anyway. Just print a sample of your work, and the most important facts and figures. That's what I did with mine, and then included, at the bottom, an URL where they can go for more details anent the promo, as well as read the terms and conditions. Leading them to my website will expose them to more of my work, helping them decide if I am the photographer they want. Then they can either ring me up or E-mail me and then we can talk and schedule a consultation.
Like any other strategy/campaign, however, its highly unlikely that a lot of people will respond right away. But at least you've hopefully registered in their minds and, if you follow up with another mail piece weeks later (or even with a call earlier than that, 'hey, did you get my mailing?'), the chances of them hiring you will increase.
Another thing I've done is to print post cards. I can either mail these or give them to people, just like I'd do with a business card. The advantage of the former over the latter is that you can display a number of your pictures versus just one or none, depending on your business cards' design.