SFGate recently published an article regarding job search habits. It’s worth a read…
http://blog.sfgate.com/gettowork/2012/10/15/do-you-have-these-five-job-search-habits
However, the # 1 habit that should be listed prior to all others is research,accurate research. Be prepared before you implement persistence and follow up. We have plenty of people who are mastering persistence and follow up but failed research, meaning they did not research our areas of specialty prior to reaching out. Make sure the search firm that you have selected specializes in the space that you are looking to find a job and that they fill positions in your compensation range. Understand as well, retained search firms work for client companies and are compensated by client companies which means if you do not fit an existing opening, you will not take top priority.
This is also true when responding to job postings. Persistence is great if you have done the research on the position prior to continuing to follow up with a job posting that you are not qualified for. We have people daily continuing to follow up on openings that they are not qualified to do. This actually makes a worse impression as if shows lack of research and judgment. Make sure you research the search firm, understand the firms specialties, and make sure the firm fills positions in your compensation range. If you are not hearing back and are frustrated with non responsiveness, take a look at why that is prior to continuing to follow up
If you are persistent but have not done your research, you look unprepared, which may be eliminating you from consideration from the beginning.