I am quoting a colleague of mine:

               In selecting letter writers, they should look for people who can flesh out the entries on the CV.  We don’t need letters which simply parrot back the CV or tell us what a wonderful person the applicant is.  Rather, letters written by people who can critically evaluate the applicant’s research or discuss the substance of his/her service contributions are especially valuable.  Don’t pad the packet; we never want to see photocopies of the hand written green sheets.  There is no sense in pointlessly killing trees.  If the applicant provides a summary research statement, an explanation of the candidates’ research that is accessible to the generally educated layperson would be appreciated.  Also, in the case of articles that have a football team’s worth of co-authors an explanation of the candidate’s contribution to the research would be valuable.  If the applicant has articles that are under initial review (or in the revise and resubmit stage), please tell us where.  These are a few random thoughts.  If I come up with more, I’ll send them to you.