The best and worst things to put in your cover letter, according to 9 HR experts

We asked career experts and hiring managers what cover letters have left lasting impressions on them, and they shared the best and the worst cover letters they’ve ever seen.

In today’s applicant-driven job market, an “optional cover letter” isn’t actually optional.

While your resume is meant to summarize why you are qualified for a role, the cover letter is what shows the employer why they should want you at their company. This is where an applicant can showcase their personality beyond a bulleted list of previous job titles. Strong cover letters portray a mix of your character, enthusiasm for the role, and unique background that qualifies you for this job above all others.

While you want to stand out, some candidates take the opportunity for self-expression a little too far. Remember, this isn’t your Match.com profile or long-awaited memoir. Keep it professional and avoid writing three paragraphs about your dog’s favorite chew toy or, like this one infamous NYU student, brag about your ability to “do 35 pushups.”

We asked career experts and hiring managers what cover letters have left lasting impressions on them, and they shared the best and the worst cover letters they’ve ever seen.

If you want your next job application to stand out from the pile, follow these “Do’s and Don’ts” of how to write a cover letter:

Do: Include statistics

“One of my biggest pet peeves when reading a cover letter is when an applicant says that he’s done something but doesn’t provide any data to back it up. You saved your clients money by implementing a new cost saving system? That’s really great, but how much did you save them? This lack of really important information leaves me questioning how impactful the applicant’s contribution really was. In order to truly make his cover letter stand out, the applicant should not only say how he is an asset but actually provide data that proves this.”

— Jacob Dayan, CEO and Co-founder at Community Tax

Don’t: Copy Paste To Every Company

“I understand that applicants are typically blasting out their resumes and cover letters to a large group of companies, and the most efficient way to do that is to use a template to write their cover letter. This is not a bad practice. However, far too often I see cover letters where the only thing that has been swapped out is the company name. A great cover letter will incorporate information about the specific company and/or specific job role. Even for job roles that are similar, the companies have different cultures and different ideals and traits that they value. With that in mind, an applicant should address those ideals and use his experience to demonstrate how he embodies those ideals”

— Jacob Dayan, CEO and Co-founder at Community Tax

Do: Make it Personal

“One of the main things that I look for in a cover letter is personalization and a clear and concise format. While it may be tempting to copy and paste the job title and company name into your letter and send it off, no job is the same and neither will each cover letter. Doing a little extra research to find the name of the hiring manager can make a difference in the cover letter as well as tailoring your previous work achievements to that of the job description. This helps you create a better structure for the cover letter-talk about the business, you, and then circle back to the business plus you.”

– Dana Case, Director of Operations, at My Corporation

Don’t: Tell Your Life Story

“Once I was going through candidates for a position and in one of the cover letters I had an applicant talk about her journey through life. Her mission in life and her general outlook on the bad things in her life she wasn’t shy about getting specific. A part of me wanted to meet her out of a weird curiosity, the rest of me knew that with a cover letter like that she’d never get hired. Her cover letter told me most of all that she was someone who liked to talk a lot, and worse, she thought she had a lot to say. In my experience, the people who have a lot of wisdom don’t advertise it, because they don’t know that they have a lot to say and would rather observe lessons they learn from other people.

Whether on a cover letter or on a resume. Keep everything short clean and to the point. If people want to know your life story, and or, philosophy don’t worry they’ll ask, and that’s not meant to be sarcastic, some employers will ask. However, it’s not information you should willingly volunteer it says things about you that you may not want to be associated.”

— Nate Masterson, Marketing Manager at Maple Holistics

Do: Include a Letter Even if It’s “Optional”

“If a cover letter is suggested or required, provide one. You’d be surprised how many people don’t provide a cover letter, even when one is requested; in my experience 65% – 75% of job seekers do this.”

— Nate Masterson, Marketing Manager at Maple Holistics

Don’t: Forget to Address the Hiring Manager

“A [bad cover letter] has a single, gender specific salutation, i.e. Dear Sir or Dear Sirs or even Dear Sir or Ma’am. If you don’t know who you’re writing to, be generic; Dear [Company Name] Team, for example.”

— Greg Szymanski, HR Director at Geonerco Management, LLC

Do: Research What You’re Applying For

“The worst cover letters are the ones that are mass produced. Addressed to “Dear hiring manager” shows that the applicant has not done adequate research on who is making the hiring decision. There are too many sources today to not find out.

Not addressing how and why you are qualified for the actual job that is being hired for is another major mistake. It’s important to illustrate how and why you are suited and deserve an interview. It’s important to really read and comprehend the job description so you can address how you can meet those needs. Share examples with measurable results on what you have done, how you did it and how it helped the employer.”

— Laurie Kahn, Founder/CEO, at Media Staffing Network

Don’t: Include Your Headshot

“I’ve seen incredibly short cover letters with just an awkward photo attached to them for no reason at all, staring at me silently. Others were written in a surprisingly terrible English which is why they sometimes revealed quite dark and inappropriate things (“I will work you”). And some would overshare about why they left their previous jobs or about how incredibly awesome they already are at what they want to do.”

— Laurie Kahn, Founder/CEO, at Media Staffing Network

Do: Be Unique

“When it comes to the best details, those that really make you like that person instantly, I’ve only seen a few of those over the years.

The most recent one came from a runway model who fell through a ceiling onto her head and neck. She survived a traumatic brain injury and had to learn to walk and talk again. And then she used her passion for acting to figure out how to remember again. She was a true survivor and concluded her cover letter with a simple “Let’s do great things together.” I mean, how do you not want to work with someone like that?

Personal details like these show determination, willingness to do the hard work and never give up. They put weight behind your claims of having certain qualities, whatever they are. And they also make any candidate memorable. I always encourage job seekers to share something interesting about themselves. You just need to be careful not to overshare.”

— Tomas Ondrejka, Co-founder & CMO at Kickresume

Don’t: Get Overly Wordy

“The worst cover letters are long – I’ve seen 5 page epistles! Keep it simple and get to the point or you’ll quickly lose the attention of the Recruiter. It’s also inappropriate to include personal details like a photo, your age, your family situation or your hobbies. You may enjoy zombie role playing games, but if the information isn’t relevant to the job, leave it off. The most entertaining cover letter I’ve ever seen included a David Letterman-type Top Ten List of reasons he should be hired. #1 was because I have a great sense of style and an even better sense of humor. Unfortunately, the position we needed to fill was an Accounts Payable Manager, not a comedian.”

— Julie Cox, Talent Acquisition Leader at AECOM

Do: Provide All Contact Info

“Include contact info: phone number, email address and city with state as a minimum. Also, be specific about what position you are applying to and make sure you have changed it from the last cover letter you sent!”

— Linda Ferrante, VP Operations at RFT Search Group

Don’t: Be Overly Artistic

“Don’t get too crazy with graphics and colors! If it’s too busy, people can’t read it. Unless you’re in a creative position or industry, simple is better.”

— Linda Ferrante, VP Operations at RFT Search Group

Do: Be Concise

“Too many job applicants seem to miss the point of a cover letter entirely. It’s really just a bite-sized sales pitch that convinces the reader to take a look at your resume. You want some of your personality to come through, but don’t be so casual that you can’t be taken seriously. I once received a cover letter so pretentious and wordy, I thought the candidate must have accidentally sent me the first draft of their autobiography. Being overly self-aggrandizing is an immediate red flag to hiring managers and it’s a guaranteed way to have your application tossed aside. Additionally, some of the best cover letters I’ve seen have been short and to the point. The candidate didn’t come across robotic, but they wrote in a polite, professional tone and just mentioned a few examples of their background. That was all it took to get called back for an interview.”

— Lauren McAdams, Career Adviser & Hiring Manager at Resume Companion

This article was originally published on Kununu.com.