With this rampant librarian shortage 😉 and all, it helps to have all your stuff together when applying for a new job. Christine over at NextGenLibrian has a pretty good write-up of what to do and not do with your cover letter.
I have served on a couple of search committees, and it truly is an educational experience to see how others promote themselves. You definitely learn a lot about what sells and what doesn’t by looking at a bunch of resumes. The tips at NextGen are definitely good food for thought for anyone looking to polish up a letter.