The following two articles are a "must read" for everyone who will need to write a cover letter, now or at some time in the future. (That's you, right?)
"Dear Dr. Neufeld" from ScienceCareers is written by a professor from the University of Waterloo who has grown frustrated with the letters of inquiry he has received from students seeking a position in his lab. While the article is aimed at undergraduates considering graduate school, many of the same principles apply when you're seeking a postdoctoral position! In the article, Dr. Neufeld provides an example of a well-written letter, then he dissects the letter carefully to explain the significance of individual phrases and sentences.
In "15 words to eliminate from your vocabulary to sound smarter" from The Muse, Jennie Haskamp takes an edgy approach to explaining how words like "very" and "really" and "irregardless" undermine your writing and your credibility. The article isn't about cover letters specifically and you can apply the ideas to all of your professional communication.
If you would like feedback on your cover letter, please bring it to our weekly CV/resume drop-in clinic!