Job-seekers often neglect their cover letter, but that's a potentially fatal mistake when it comes to actually landing an interview.

Not every job application asks for or gives you an opportunity to submit a cover letter. Some online applications just want a resume, or for you to fill out various forms. When you have a chance to offer up a cover letter, however, you should take it.

Use the document to show some personality and to fill in details about yourself that aren't obvious from your resume. Consider this document a way to make yourself stand out in a sea of similar applications and resumes.

A person holds a blank piece of paper.

A cover letter is a blank slate that you can use to show the person hiring who you are. Image source: Getty Images.

1. Always be unique

The person doing the hiring will know if you are using a generic cover letter you submit for every job. Don't fall into that trap. Instead, customize your cover letter each time by addressing a specific point (or points from the job listing).

That only takes a little bit of effort, and it shows that you actually want the job. If you go generic, it makes the hiring manager wonder if you're simply applying for every opening, and that may make him or her consider your application spam.

2. Address any holes

If the job requires skills that are not obvious from your resume, use your cover letter to spell out how you have what's needed. Maybe you've never held a job with "sales' in the title, but have been involved in selling stuff. Explain that in your cover letter.

The same is true of added skills. If you speak another language or can code but neither was ever part of your job, make that clear in your cover letter.

3. Connect the dots

How bold you should be in your cover letter depends on how good a fit for the job you are. If it's clear you are qualified from your resume, use your cover letter to reinforce those points. If you're reaching or don't meet all the traditional qualifications, then connect the dots -- be bold and explain why your non-traditional background makes you perfect for the job they are hiring for.

Be yourself

While a cover letter should be a formal document, it does not need to be a lifeless one. Use it to show the person doing the hiring a little bit of your personality. That could mean working in a line about a hobby of yours that's relevant to the job, or it could be using a bit of humor.

The goal of a cover letter is to make the person reading it want to interview you. Remember that the people that are hiring often read dozens of cover letters and resume in a row. Make sure yours stands out by being interesting and showing your connection to this specific job.

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