See the document below for our intro guide and an example cover letter.
At it's core, a good cover letter addresses the question of "Why?". Why You? Why this job? Why this company? While a resume will list your skills and experiences, your cover letter should take those and make explicit connections to the companies needs, goals, and values. Recruiters don't want to work hard: do the work for them and make those connections clear and explicit.
Another great use for a cover letter is to showcase your passions and values, especially more nuanced ideas that may not be obvious in your resume. Look to the position description and the company mission, and use those to highlight where your values align with the company. This is also a great way to showcase that you have done your research, so be as specific as possible.
Unless a length requirement is specified in the application, your cover letter should be about one page with 3-5 paragraphs of main content.
Probably not. Creating unique cover letters is a lot of work; it's best to submit a cover letter if it is required for the application or if it is a position you are very excited about.
You can often reuse your opening and closing paragraphs in a cover letter but the middle paragraph is used to show how you would be a good fit for the company's position. This is where you want to include specific details from the position description and tie them to your experiences and skills; as such, your middle paragraph should be pretty unique to each company. When reusing any part of your letter, remember to change the company name and other identifying information.
Not necessarily. These days a cover letter might be an email to a hiring manager more so than a PDF submitted through an application. What's most important is that you always include a professional opening salutation as well as your full name and contact information.
If you would like to use a formal style, a good place to start is cover letter templates in places such as Word or Google Docs. (If you used a particular resume template, there are often matching cover letter templates!)
It's always great if you can address the letter to a specific person, but if you don't know who will be reading it you can always go with 'Dear Hiring Manager' or 'Dear *company* team'.