Cover letters should be simple and to the point -- they are not college admissions essays, and they should max out at half a page. A good cover letter concisely explains how your skills and experiences align with the most important qualifications of a role. A great cover letter includes all that and a little "something extra" -- a single sentence that explains why you'd be a great fit.
Employers want to hire people who are excited about working for them, but they're not going to assume you're legitimately enthused simply because you sent in a resume! They also don't want to spend valuable time reading a suck-up style sonnet about how great they are -- they know they're great and are trying to determine if you're qualified. That's why you just want one simple sentence at the end of your opening paragraph indicating what moved you to apply in the first place.
The best version of this sentence is something specific, like calling out your alignment with the company's mission. For instance, if the company is dedicated to social justice, and you've been volunteering at an organization dedicated to social justice for years, mentioning the connection will give context to your enthusiasm, show that you might bring some useful knowledge to the team, and indicate that you’ll be committed to the company’s work. Or maybe you're passionate about the genre of content the company produces -- if you wrote your senior thesis on the impact of science fiction on real-world technology, it's a no brainer that you'd be applying for an assistant role at a production company specializing in sci-fi! If there's not anything that specific -- either because the posting is too vague or your interest in the company is more broad, that's okay, too. Explain what led you to apply, even if it's just as simple as "I'm looking to take the next step in my career as a creative executive at a network."
A different way to include this "something extra" is to highlight an element of your personal or work history that could bring added value to the company, regardless of whether it’s listed in the job posting. Perhaps you are a non-traditional candidate, but the work you’ve done in a different industry (or side of the industry) will give you perspective that a more obvious candidate might not possess. For example: Someone coming from the healthcare world who wants a writers' room support staff role on a medical drama would bring knowledge to the room that someone with a purely entertainment background wouldn’t have. The thing that sets you apart won’t always be that apparent, but considering that no one has your exact work and life experience, there’s always something to draw from that could help you stand out. Think about what you could do for a company that they might not have even realized they needed, and make that argument in your “something extra” sentence. Just make sure it’s relevant!
But remember: We're talking about one sentence -- not a paragraph, a lengthy diatribe, or a bullet list. The bulk of your half-page cover letter should be about your qualifications for the role, and you want to make sure that information isn't buried too so far down the page that the hiring manager never gets to reading it. Keep it short, simple, and specific, and you're good to go!
-- Angela Silak & Cindy Kaplan