Having gone through many searches over the last few years, I’ve developed a list of hints for job candidates (both faculty and administrative). If they seem obvious, you’re in good shape. If they don’t, PLEASE print them out, keep them, use them.
Proofread! There is simply no excuse for typos, poor grammar, or geographical howlers in a cover letter. (At my old school, also in the Northeast, we had a candidate who declared in the second paragraph of his cover letter that he never applies to schools in the Northeast. That was the end of that.) I’ve seen far too many Ph.D.’s send letters that look like they were written by distracted high schoolers.
Respond quickly. We are sometimes up against external deadlines of our own, and I’ve seen otherwise-viable candidates get rejected simply because they missed the window. (Corrolary: never, never, never take seriously the announced deadline. Always beat it by a wide margin. For reasons I’ll never understand, I’ve seen far too many committees jump the gun and simply lose patience with applications that arrive at the last minute.)
Don’t cop an attitude at the interview. You may, in your heart of hearts, think that my college is beneath you. I don’t, and the professors here don’t, either. We will not be intimidated. If you think you’re doing us a favor, don’t do us any favors.
Check the college website! If you couldn’t be bothered to do a little preliminary scoping, I get the message that you aren’t serious about working here. Ask questions that show that you’ve done your homework.
Don’t trash your previous employer. Even if everything you say is true (and it may well be), we’ll wonder if it just reflects a hyper-critical or high-maintenance personality. Even if you’re escaping a sinking ship, make clear that the attraction to the new position consists of more than ‘it’s not the old position.’
Keep it mind that, appearances notwithstanding, it’s not all about you. I’ve had interviews with intelligent, accomplished, charming, winsome candidates I couldn’t hire. At the end of the day, it’s about what the institution needs. If that’s you, great. If not, it’s not usually because of anything you could control. (Exceptions: if you commit the gaffes above. The cover letter gaffe will prevent you from even getting to the interview stage.)
Good luck!