A cover letter is a letter that "covers" your resume. Great cover letters meet many important purposes and offer both you and the employer several benefits.
Indeed, you taking the time to write great cover letters is one of just a handful of crucial factors in your job search and career development success.
I'd like to take this opportunity to offer you the same helpful information that I've provided to hundreds of my clients about how to consistently and easily write great cover letters.
Is a Cover Letter Really Necessary?
Many times in my career, clients have asked me, "I usually just apply for jobs using my resume only. Do I really need a cover letter?!
Without a doubt, my answer is always Yes!
Why? I'll give you 8 excellent reasons why you need to learn to write great, customized or targeted cover letters for each and every job you apply for.
1) Sparks Initial Interest and then Maintains It
The job search is a stage-by-stage process. The purpose of the cover letter is to spark initial employer interest in your application for the posting, and then get her to turn the page to briefly consider your resume before deciding whether to further consider your application.
For many postings - particularly well-advertised postings - it's a very competitive process. It's often a very brief assessment or "screening process" through which employers quickly and quietly eliminate as many applications as possible, in the shortest possible time.
So without a cover letter, you may never even get the employer's attention. On the other hand, with a well-written cover letter you can gain and maintain the employer's attention all the way through to the job offer and beyond.
2) Forms a Positive First and Lasting Impression
Great cover letters give you a golden opportunity to make a very strong, professional, persuasive first impression upon the employer. It's the stimulating, persuasive content of the cover letter combined with professional page formatting that convinces an employer to read your resume in the first place.
For job postings of many occupations, a resume without a cover letter is often just plain ignored by those who are paid to read it. A resume is naked and vulnerable without a cover letter. It needs the protection of the cover letter because there are certain things that a cover letter can do that a resume just can't do.
3) Presents Your "Game Plan" of How You Meet the Employer's Needs
As author Wallace Wattles reminds us, you must give employers what they want before they will give you what you want.
In fact, employers don't care in the least what you want until you demonstrate that you care what they want. Great cover letters get this off to a great start when you make it clear that you know, care about and can easily meet the employer's needs.
For each job application you send, you want to focus on between 1 and 3 key messages explaining why you are the best candidate for the position. You can convey them clearly, consistently and repeatedly starting in the 1st paragraph of your cover letter and then again in your resume, interview and thank you letter.
This is like a "game plan" for a professional sports team. No sports team plays without first developing a strong and specific game plan, and this applies equally to job searching.
The cover letter allows you to briefly yet effectively express your most impressive qualifications that overlap with or match the qualifications listed on the job posting.
4) Engages the Employer through Telling a Fascinating True Story
Everyone loves a good story. That's a universal truth, and applies as much within a cover letter as it does when you're telling a funny joke to a group of old high school or college friends.
We're all captivated by stories. and in the cover letter you can use the 2nd paragraph to tell your own unique story by giving a detailed, specific and concrete example of your greatest professional accomplishment to date - one that's relevant to the duties of position you're applying for.
This forms the main body or "meat" of the cover letter, and the key evidence in support of your job application.
This is in stark contrast to the resume which is often dry, dull - honestly quite boring despite everyone's best intentions to make it exciting and engaging to the reader. Stories are a lot more interesting than "laundry lists" - also known as resumes :-).
Like other great stories, the best resume cover letters captivate their readers - primarily by telling them a brief, concisely-written narrative that clearly describes the applicant's career highlight in 6 lines or less.
5) These Stories Help Employers to Visualize You Successfully Hired
Resumes don't engage the reader's imagination nearly as well as outstanding cover letters can. A well-written cover letter will help employers to visualize you in their mind.
They'll be more likely to be able to see you sitting there at your desk or wherever you'll be working at their organization. This added credibility is another key advantage to writing an effective cover letter.
6) Great Cover Letters Use "I Statements" to Build Relationships
Resumes don't build relationships. They're not personal, and they're not warm in any way, despite our best efforts and intentions. But great cover letters are!
You can use the pronoun "I" frequently (but not too frequently) to warm up your job application in your cover letter - to be "personable" without becoming too "personal."
"I" helps you to start building genuine positive rapport. This is particularly true in the 3rd paragraph when you talk about why you want to work for that particular employer and why your resume is such a great match with their job description.
7) Actively Demonstrate Many Vital Skills
I also want to mention that great cover letters pro-actively demonstrate a variety of work skills directly to the employer.
Rather than just saying that you have great skills, demonstrate them to employers right off the bat. That's much more impressive and believable!
These work skills include writing, editing and proofreading business letters, excellent attention to detail, strong organizational skills, ability to prioritize and condense relevant data or information, typing and word processing skills, professionalism, and the list goes on and on ...
8) Make it Easier to Explain Transferable Skills
If you're changing careers or looking for a "survival job," it's often a challenge to explain how your previous skills, experience and education are transferable to the new job or career.
Employers also sometimes have difficulty understanding this from looking at your resume alone. They can get "tunnel vision" and interview only applicants whose applications are an obvious match to the job posting, even if you have much to offer them.
They need you to point it out - to explain to them in specific, concrete, black and white terms exactly how your previous skills, experience and education in another field prepares you well for this new role. And you can only do this effectively in your cover letter - relying on the resume to do this for you is a high-risk venture.
Having read your explanation in your cover letter, they're more likely to also consider the content presented in your resume to be transferable as well, and offer you an interview for the position.
Great Cover Letter = Great Job
For the many reasons offered above, great cover letters play a huge role in helping you to get a great job and build a fulfilling career.
I strongly encourage you to learn how to write an effective, customized cover letter for each and every position you apply for, to ensure success in your job search.
Eric Weir holds a Masters Degree in Social Work from the University of Toronto, Canada and offers over 6 years of employment and career counseling experience to clients of all ages and walks of life. Eric publishes other articles at his website, http://www.job-search-coach.com.
In this Program Interviewees will learn and improve skills to achieve results. How to assess a candidate's background, experience and skills is important but to be able to communicate those essential topics at the right time and only as extensively as necessary is imperative. 
