There is no sure fire way of getting a response but a follow-up call always helps. If the contact person’s number is not on the job posting try a search in the yellow pages. It is worth a shot and you may get to talk to someone that can help you. Some companies have a database full of resumes from those who responded a job posting. Ask them if they can find your resume and take a look at it to see if you are a fit. If not, ask if you can follow-up with them every few weeks. You keep your name fresh in their minds and eventually an opportunity may become available.
When I recruited I asked people to call me back every couple of weeks. One of the reasons goes back to my blog on “keywords.” If you do not have the “keyword” in your resume the recruiter is searching for your call may be what gets you the job.