From my favorite site, Lifehacker:How to ensure a response to your email
Friend of Lifehacker Eszter Hargittai details how to write emails to strangers that will get a response. For example:
Write a clear and descriptive subject line. The reason for carefully crafting the subject line is two-fold. First, you want to make sure your message is not filtered out by a program as spam. Second, you want to make sure the recipient does not delete your note manually, assuming it is unwanted junk mail.
The above may seem obvious, but in our efforts to keep up with the flood of email here at Lifehacker, you'd be surprised at how unclear subject lines can get (and how many times subjects are completely empty). The article is aimed at academics, but the tips are applicable to anyone writing an email to a stranger looking for help. If you've got your own bag of tricks, let us know how you handle email to strangers in the comments.