I'm the chair of a search committee this year (not for the first time), and I started reviewing our applications last night. I am really surprised by how few of the applicants read the ad. We advertised for an open research area position but clearly indicated there were classes we wanted the person to cover. I would say only 1/10th of the applicants actually directly addressed this in their packet. Also, it is so clear that people were just using the same letter without making any modifications. Some would say I am applying to your position in Social Psychology, except we were not advertising for a position in Social. Others would say I would be an excellent fit at [insert university full name] because of my experience in….and then they list a bunch of stuff that has nothing to do with the job ad.
I realize no one is going to write a different letter for every school, but leave space in your letter to add something. I have been on the job market three times over my career and received offers every time. I had two versions* of my application, one for research universities that listed research first and in more detail and one for teaching orientated schools with teaching first and with more details. Other than the name of the university, I had 3 blanks. One in teaching, one in research, and in my last paragraph. In the teaching I directly addressed courses they wanted taught (if any were mentioned, if not, just my generic list). In research I mentioned how my research related to anyone in the department or I had a statement about how I would bring in a new and exciting topic. And then my finial paragraph I would make a comment about how I desired living in whatever town because of some reason (usually close to family and friends) or make a comment about the excellent reputation of the department.
While I did not do this, we have typically been impressed when a candidate mentions something very specific where they clearly read our website. For instance, they mention a specific concentration and use our exact wording or they mention a particular class that we teach that is not typical.
*Actually, I had 4 versions. 2 sets for those that asked for a teaching and research statement with a shorter cover letter and detailed statements, and 2 sets where everything was in the cover letter (not as detailed, but enough info).