Domain Acquisition

I often find myself sending dozens of emails a day to domain registrants about the possibility of purchasing their domain from them. I'd say less than 1 in 10 of them get back to me (often asking for a ridiculous price). Is there some sort of other way to contact people other than looking them up and attempting to email them? Are there any ways to help and assure that they get my message. I know it's often the case that people buy domains and then go AWOL from the internet, but are there some terms that can help?