Evan Schaeffer from St. Louis has two blogs, The Legal Underground and The Trial Practice Tips Weblog. He has written three posts on the latter titled "15 Ways to Ruin a Deposition." Here is his latest and last post (Part 3) on the subject. Here is a link to Part 1 and Part 2.
A sample: "Failing to incorporate your completed deposition into your overall trial plan. After a deposition has ended, do you add the transcript to a giant stack of depositions sitting on your floor? There are a number of other more sensible post-deposition steps you can take. You’ll find seven of them here: ‘Trial-Planning Steps to Take After a Deposition Has Ended.‘"