Technically, there are hundreds of ways to sabotage (literally) a job search campaign, but for the purpose of this discussion, I will restrict myself to three common mistakes most job seekers make that keep them unemployed.
A few good examples of mistakes in conducting a job search. I'm not a huge fan of over-worked resumes since resumes don't get job interviews. However, the issues of conducting a passive job search and not measuring yourself on key indicators are spot on.
Barry Deutsch
IMPACT Hiring Solutions