Back a decade, I was in the staffing industry. Some people call it headhunting, others placement firms. A challenging time when I really grew as a talent specialist. A great time to have tonnes of hiring experiences, good, bad, and ugly.
I ran across a great web-site doing some research this week, advertising a book called Headhunter Hiring Secrets by Skip Freeman. I don't own the book nor have ever read it. But, he has 21 free articles posted on this page http://www.headhunterhiringsecrets.com/SpecReports.html.
I agree with his fundamental point - that if you behave traditionally (see a job on a job board, apply through the job board, wait for a reply), your chances of getting a job are low. He has tips and tricks how to be more effective. I think he overstates, exaggerates and is too aggressive but the essence of all the articles is based on recruitment industry truisms.
Here is a great graphic from his article Why Job Boards Often Hurt More Than They Help http://www.headhunterhiringsecrets.com/JobBoards52210.html