Why aren't you hearing back
One of the hardest things about job hunting is the lack of feedback from employers. Sending out dozens, if not hundreds, of applications and emails and getting no response, not even an email to acknowledge receipt of your resume, is frustrating and demoralising. While there is no way to get a response for every application you submit, there are ways to increase employer interest.
As a hiring manager I would not follow up with a candidate if his or her resume or cover letter had even one spelling mistake, wrong word or typo. And getting the details of the employer and the position you are applying to wrong is a great way to have your resume overlooked. It shows lack of attention to detail.
Tailor your resume and cover letter
Hiring managers know when you send them a generic letter. Tweak your resume and cover letter to convey your interest in their job and their company. Use the job posting and the company's website to include information that is relevant to them. Alternately, you may not be hearing back from an employer not because they didn't like your resume, but simply because they used a computer program to sort resumes based on keyword content and yours never came up. Tailor your resume to use words that are in the specific job posting.
Follow application instructions
Many job postings have specific instructions on how to apply. Follow these instructions! Hiring managers will rarely look at resumes that are not submitted in the way they specified.
Apply within your means
Job requirements in postings are often ideals; the candidate should ideally have 3-5 years' experience herding cats. It's perfectly reasonable to apply to positions that you are not exactly qualified for, but don't be surprised or discouraged if you don't hear back from employers. Applying for jobs that match your experience, goals and background will bring you more results than always applying to your ideal.
Reassess your job-search plan
If you've reviewed your applications and everything you send is perfect, clear and convincing but you are still not getting much response from employers it's time to change your perspective and approach to job hunting.
The most effective job hunting approaches use multiple techniques, like online applications in addition to cold calling businesses you're interested in, or networking at events. If you are focusing on positions you're interested in, try approaching companies you'd like to work for. If you're broadly applying to every HR position, try narrowing you search to a specific field.
Not hearing back from employers is discouraging but is not a personal rejection. In all probability there are several hundred applicants to the posting, which means that hiring managers look for any small reason to narrow the pool of candidates. Ensure your applications are effective, error-free and relate to the position you are applying to and eventually you will be successful!