Your résumé is a concise summary of your accomplishments, experiences, and skills. Your cover letter is your opportunity to explain to each hiring manager how those accomplishments, experiences, and skills can add value to their organization.
Simply put, a cover letter gives a compelling reason for the hiring manager to pursue an interview with you. A cover letter should always accompany your résumé.
The more you customize your cover letter to the specific needs of the organization, position, and industry, the more effective your cover letter will be. Creating a "general cover letter" to use for multiple positions will not be effective. Instead, look at the job description, identify what's important within it, and make sure what you write speaks to these points.
What To Include In Your Cover Letter
You should write your letter in a business format—and it should fit on a single page. Most cover letters are comprised of four paragraphs. Here's what you should include in each section:
Addressing a person is the first step to customizing your letter and standing out from a pool of applicants. See if you can find the hiring manager's name on the company's website, LinkedIn, or through a different online search. If you can't, "Dear Hiring Manager" is a good alternative.
This is your introduction, so keep it short and direct. Tell the employer the name of the position you're applying for and where you saw it posted. If you were referred by a current employee of the company, be sure to include that person's name and title.
Explain how your accomplishments, experiences, and skills are a match for the position. Refer to the required skills section from the job posting to stay focused on the most relevant information. You don't have to address all the qualifications. Pick a couple that let you best illustrate your skillset. Making this connection is important—especially if you don't appear to have a lot of directly relevant experience on your résumé.
Demonstrate your motivation. Aside from the fact that you saw the job posting, what draws you to this position or company? Remember, let the employer know what they can gain from hiring you—not what you want from them.
Let the employer know you are eager to interview, and include contact information. You can also include steps for follow-up—just be sure to follow through.
You can't lose with the traditional "Sincerely."
Covering Your Bases
The structure above outlines a standard cover letter. But in addition to customizing your letter to the job description, you may want to tailor it by industry as well. Applying for a more creative job? A less traditional cover letter may be better. Want to be a writer? Consider your letter a sample of your work—which means be extra sure to proofread.
If you have contacts in your desired industry, ask them what type of cover letter might connect best with their peers. See if they'd be open to reading yours and providing you feedback. You can also get some inspiration by looking at examples of cover letters for different industries (from marketing to finance) here.