Let’s state this up front: Cover letters are confusing. Even the name is odd, sounding way more pen-and-paper than it is in actuality. But despite the anachronistic term, a good cover letter is just as crucial as your résumé itself.Here’s why: It touches on multiple super-crucial skills, even before the first interview. It shows off your writing skills, displays your email etiquette, and is basically the online version of an elevator speech — your chance to show off your most professional, most intelligent, most hirable self. And it should be a total win. After all, you don’t have to worry about nerves the way you do in an interview. You have more space to elaborate on any achievements or skills you want to highlight on your résumé. And you also have a chance to explain, in your own words, why this particular job is the perfect one for you.But here’s the flip-side: Your cover letter also has the power to take you out of the running as a candidate. Even a simple mistake, like sending it as an attachment instead of pasting it into the body of your email, can result in your entire application being overlooked. You do not want that.That's why we asked career experts and hiring managers to weigh in with their tips for crafting the perfect cover letter. Ahead, 30 dos — and don'ts — to consider before you hit send.