Make the witness go on tilt
A good litigator is always trying to get in the head of the opponent. Like a great poker player, you not only want to know what the deponent is thinking, you want to get inside their head. In poker terms, you want them “on tilt.” When a poker player (or deponent) is “on tilt,” they can’t think straight. They may get angry, or frustrated, and start acting recklessly. You don’t want to have the witness become comfortable. You want them to be uncomfortable, because they’re going to be more likely to agree with you and be cooperative. They'll want to get out of their uncomfortable situation by ending the deposition.
Don't be predictable
So how do you make the deponent “on tilt?” I’m not talking about making it hot in the room or being rude with them. One way you can do it is by not following a predicable order of questioning during the deposition. When you ask a set of chronological or linked questions, you allow the witness to get comfortable with what’s coming next. They anticipate questions, understand where you’re going, and have an easier time giving the rehearsed answers. When they don’t know what’s coming next, they become mentally uncomfortable. If you follow a chronological, or similar predictable order, then it’s much easier for them to keep their story straight, even if it’s not completely true. Through proper planning, you'll be able to go from one topic to another, back to another, back to the original topic, effortlessly. You’ll have your outline and documents ready. The witness doesn’t know this, and will have a harder time keeping their story straight.
Wear the witness down
Another technique, which I discuss in this post, is to wear the witness down. Deposition stamina is something that few witnesses have, so if you can bide your time and circle around the key topics enough then eventually your witness will be worn down and might finally give ground on the key point. It's the same effect as a long mediation. By the end of the day people are more willing to give in because they're tired and want to be finished.
Cover an embarassing topic
A final technique is to make sure you cover topics that are either personally embarrassing for the witness or make them upset. This is a fine line because the discussion needs to be related to something relevant to the case. If you're in a breach of contract case, for example, then a discussion about the witness's infidelity probably isn't relevant and will draw objections. But if you have examples where the witness made mistakes in their capacity as a key employee for the opposing party then raising those mistakes will make the witness uncomfortable and certainly less likely to want to battle with you on other points.
Whatever your method, if you discover that you can keep the witness off balance, cover topics that they don't like discussing, and wear them down, then you'll likely get a lot of good admissions to support your case. Remember this concept and it will pay big dividends in your depositions.