Following up on the first part of this series, I'll continue with the second five ways a lawyer can ruin a deposition. Once again, these tips are all based on personal experience, so I know them well--
6. Failing to ask the questions you should ask in every deposition. There are certain questions you should ask in almost every deposition. Here's a helpful list: "What To Ask in Every Deposition."
7. Asking the right questions, but in the wrong way. There are many ways to word a deposition question. Few of them are right. For a few explanation, see "The Anatomy of the Perfect Deposition Question.
8. Failing to listen to the witness's answers. Sometimes a witness answers a question other than the one you asked. Unless you're really listening to the witness, you might not even notice. See this post: "When the Witness Answers a Question You Didn't Ask."
9. Stopping after the witness answers "I don't know." Sometimes when a witness claims not to know an answer to your question, it excludes him as a witness on that point later in the case. Or does it? Not unless you know how to follow up appropriately. Here's a post on that topic: "When a Witness Answers 'I Don't Know.'"
10. Paying too much attention to your opponent. Opposing lawyers: who needs them? Sometimes it's best just to pretend they're not there. See this post: "Ignore your opponent in a deposition." (But also see "Depositions: Don't Ignore Form Objections.")