Writing too much

While it is important to showcase your personality, having multi pages for a cover letter is not a good idea. Recruiters (gatekeepers) these days do not have the time or resource to go through each candidate's resume and overstretched cover letters. "I encourage people to stick to one page. And because people have short attention spans today, and less time to read each cover letter in full, I suggest writing in bite-sized nuggets or bullet points." said Nicolai.
Addressing the letter to the wrong person

Addressing your cover letter to the wrong person is by far the worst mistake one can ever make.  If give a sense of irresponsibility and lack of attention to details.  Therefore it is important to note the addresser, if the name is not provided  omit it and list your name and targeted position.

Not tailoring the cover letter to the company or job you're applying to

Hiring managers have probably gone through a room full of resumes, by now they can easily identify the generic 'one size fits all' format from a cover letter writer by a candidate.  "Customize each cover letter targeting the specified job description. A master cover letter is fine to use as a template or outline, but always remember to tailor It." advised Nicolai.

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