You will be much more successful if you simply put a little effort into your job and stop pissing people off. Here are some ideas:
If you are recruiting candidates who reside in the United States for positions located in the United States, do not offshore your cold calls to India.
If you find my résumé with a keyword search on the job boards, take ten seconds to see if my location, skills, and experience are actually a match. Pushing some three-month junior/entry-level contract in New Jersey on someone in Salt Lake City with 15 years of experience is a good way to piss them off.
If you call me, I will most likely not answer if I do not immediately recognize your number. If that happens, do not call over and over again. That is called harassment and will get you reported to the authorities. Please leave a single voice mail. If I do not have a pre-existing personal or business relationship with you, do not mark that voice mail "urgent." That is unprofessional and annoying. If I do not return your call, you may interpret it as "not interested," after which I would appreciate if you would stop calling.
If you email me, do not use some crappy form letter. Feeling like just another database record does not exactly give me the warm fuzzies about your agency or the companies you represent. But if you must use a form letter, at least try to customize it with my information. Few things turn me off faster than reading "Dear Consultant" at the top of an email. As with phone calls, if I do not respond to your email, you may interpret it as "not interested." If you continue to email me, I will blacklist company’s domain name and report you to SpamCop.
You will eventually learn as I have, that in career matters, it is the relationships that are most important. Fail to build and nurture those relationships, and you will fail to attract the best talent. Yes, it takes effort. No, it is not easy. But follow these simple guidelines, and you will see considerable improvement in the quantity and quality of your placements.