Looking for a job is a full-time job -- one that can be daunting, overwhelming, and frustrating. Some of the best positions, however, aren't advertised. As a supplement to your active job hunt, consider a headhunter. Headhunters are employed as recruiters to find vetted talent without sifting through a thousand resumes in response to a Craigslist ad. Follow this guide to getting noticed by top he…