To me, cover letters are important, because I'm trying to build a team, not a set of replaceable individuals. A CV tells me nothing about personality, interest or motivation. It's just experience and perhaps achievements (if done properly). Therefore, I'd always look in the cover letter for those points. A good cover letter almost always led to an invitation to a job interview, even if I was still a little bit unsure of the experience listed in the CV.
Here are some DO's and DON'T's.
- Indicate clear interest in the company and the job. Display familiarity with both. This helps anyone building up a team understand that you're motivated.
- Show motivation! Help me understand what drives you, how this fits into what you want to do. Demotivation in one person can drag a whole team down, so it's important for me to understand your motives.
- Describe your qualities in a way that I wouldn't be able to glean from your CV... Else you're using my limited time to tell me the same thing twice.
- Differentiate! Help me to understand why you're different from other people. Read some bios of people on LinkedIn to help you understand how to avoid saying the same thing as others, words like "creative", "self-motivated", or "team player" are unimpressive at best and have an adverse effect at worst.
- Try to understand the type of personalities in a company, and adjust tone accordingly. This is a little bit like dressing up for a job interview. Don't be overly formal with a music startup ;-)
- Keep it concise. No more than 3 paragraphs. Remove anything that's not absolutely necessary in this very first impression. Your goal is to get invited, not acquainted. The latter will happen in the interview process.
- Attach your cover letter. Put it in the email body. If you put it as an attachment, I might just look at your CV and skip the cover letter. I really don't understand people who attach their cover letters...
- Place your future bosses too high above you. Try to address them almost like equals. You might still be just at the start of your career, but show confidence in the fact that one day, you could be in their seat in some other company (if you're reading Quora, there's a good chance you will). Disclaimer! I've lived in different countries and this is culturally specific. This works well in companies with a modern Western mentality... In a company with a more oldschool mentality, this might not go over so well.
- Place yourself above potential future bosses. Then you're just being a dick and I won't want to work with you. Go start your own company or go work in some oldschool company where such attitudes belong.
- Leave the email body blank. Nor the subject line. Else I won't even understand what you're applying for... Or if you care at all. This happens more often than you'd think. About 20-30% of the applications I got had less than 20 words in the body.
- Copy + paste the same cover letter over and over. We can tell. At least adjust the part where you show interest and motivation. Show that you care.