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The economy right now is still in recovery mode as companies are hiring but are specific in what they can do for many reasons. Often there is nothing wrong with what you are doing as applying and receiving both phone and face to face interviews are good signs that your talents are being looked at in terms of getting hired for a position. Without being in the room when you interview or listening on the phone when talking to the recruiter, here are some suggestions that you can review to see if some small changes can be made to make yourself a person any company would wish to hire.
1. It sounds like your cover letter and resume are well written but having each reviewed by someone such as a friend or former co-worker to see if they notice anything that stands out that can be changed. Could be wording as well as length as nothing more than two pages is enough as HR will bypass those resumes longer than that.
2. Practice your interview skills in front of a mirror as well as in front of family and friends. See if they notice something that is standing out and can be changed such as way you sit at a desk to pausing before answering a question.
3. When attending the interview (both phone and in person) are your professionally dressed and are you listening and showing attention when asked questions. Also are you on-time when an interview appointment is set-up (being late is never good).
4. Doing your research is key in getting a second interview and eventually an offer to join the company. Research on the company in question can be the history of the company to what they are doing in the news. These points then can be asked when the interview is over and you are asked if any questions you might have. Having nothing to say shows that you do not have much interest in the company and the job so having questions before saying thank you gives you the edge over other candidates. Same goes with knowledge of the industry that the company is in as offering ideas and news on what the industry is doing can show the recruiter that you are aware of things and knowledgeable of things within the company and who they deal with.
5. Something that people forget is to send a thank you note to each person you interview with (handwritten and not email). This little touch is something many forget as it makes the recruiter aware of you when hiring.
I hope these tips can help as do not give up on the interview process as on average it takes 6 months or longer to find a job. Please let me know of any additional questions you might have. Also if you could take a moment to rate my assistance so that I know my help was useful and allow me to receive credit for assisting you today.