Now back to the point, I agree that link building is really tough if you are running after competitors back links and also agree that most of them will not love to link back to you. But, what we can do to improve our ratio of replies:

1. Never keep your mail Subject/Title as “Link Exchange”, “Link Request” etc. rather use something like “Business Partnership”, “Be a Business Partner” and so which better fits the sites business. It seems a little Spam but at least site webmaster will give a try to read it.
2. In body of the mail like Dan mentioned, make sure to keep the matter short and eye catching. Don’t forget to give a reason why you want them to link to you and keep this part in BOLD, COLOR and CAPITAL letters so that the webmaster can understand what the mail is about really. And, in the end don’t forget to say sorry for your FALSE subject matter of your mail.

In my opinion, along with following competitor’s links, we should arrange some other great links and how I do is, please visit my blog post:
http://link-popularity-india.blogspot.com/2009/12/convert-mails-into-links-and-make-link.html

I am sure, my blog post will help such link builders who don’t know how to arrange good links via mails.

Regards,
Lalit Sharma