I have seen countless cover letters that miss the mark but the worst ones, by far, are the ones that go on, and on, and on. Cover letters are intended to pique the interest of the employer just enough to get them to take a good look at your resume. That is, if they even read your cover letter.
A great cover letter is short, direct, and succinctly states how you might help the employer, not vice versa. At most, it should be four paragraphs of four to five sentences each. As there is a better than fifty percent chance that the hiring manager will get a printed copy of your cover letter, the font size should be 11 point minimum. Remember, in most companies, the hiring manager is likely to be a lot older than you. Don’t make him or her feel any older by trying to squeeze your life history onto one page in six point font causing them to wonder if they finally need reading glasses. That’s the surest route to the trash can.
Use the cover letter to pull out two or three talents or key experiences that demonstrate how you would be a great fit for the position. Do not try to squeeze all the relevant experience from your resume into your cover letter, that’s what your resume is for. Look at the key words in the job description and use them in your cover letter. Many companies use programs to screen resumes and cover letters for key words so make sure that you’ve included them. Show how your experience demonstrates that you have the skills needed for the role and that you’ll be able to hit the ground running.
And remember, you are only trying to get a date, for an interview, with the human resource or hiring manager. Nothing is a bigger turn off than over selling yourself.