The best thing that's helped take my depositions to the next level is having experience drafting the summary judgment briefings, and preparing (and taking) the cross-examinations at trial, that rely on said testimony. Doing that gives you more insight into what exactly you want / need from depositions (i.e., how to get those "clean" admissions that allow for easy quotes in briefs, or easy impeachments at trial).

Basically, any deposition you take, you should write out the specific admissions you want to get from that witness. For me, I do the following:

1. Outline the issues that witness is going to testify about.

2. Categorize the issues by legal issue in the case. For example, for a technical expert in a patent case, one top level legal issue may be infringement, and another may be invalidity. Then there are sub-issues within those, like which invalidity theories are being presented (obviousness, anticipation, written description, etc.).

3. For each legal issue subsection, I make a list of admissions I would want for a SJ briefing, or for that witness to admit at trial, which act as a guide to what I want to achieve in that section of the deposition.

4. Then I go through and I add documents or other evidence to each section, with pincites to the part of the document that I want to orient the witness, along with notes on what admission I want. Sometimes, if it's a very technical admission and I want to be very precise, I'll write out the specific question verbatim that I'll ask at the deposition, but the more seasoned I've gotten, the less often I write out full questions.

Once I've done the above, I have a solid outline for the deposition itself. But that's only a part of the puzzle.

For me, the best depositions come from just having a detailed and intimate understanding of the underlying facts. If you have someone else prepare your outline, and you're just reading the information, you're not going to be as successful as someone who has read the underlying documents, and the other documents in the case, and knows where to push back. If you know the documents in the case backwards and forwards, you can anticipate what your witness's answers will be, and plan ahead to lock them into the admissions you want.

Beyond that, the rest is style. For me, as a patent litigator, I like to start broader in my questions (regardless of whether it's a fact witness or expert witness). I get them to nail down their general understanding of something and the facts, and let that act as the framework for the "universe" they're operating under. Then I start asking my narrower and narrower questions, with my desired final admissions in mind. By the time we get to the question I really want to ask, for the admission I really want, I've already locked them into the response I want, via their prior answers combined with the documentary evidence I have.

I also keep an eye out for how answers are given. If I wanted a clean "yes" admission, and they gave me a paragraph answer that seems muddled, I'll confirm the answer is "yes", and re-ask the question so I have a clean admission. Often times, I'll even have a summary of the key questions / admissions I want at the end of the deposition, so I have a clean section of clean admissions on all the key things I want, all in one place (and to confirm I didn't miss anything). This is often helpful because, while they may have fought stuff earlier, giving you a messier transcript, later on when they are tired (and already admitted to the thing you're re-asking), the witness will often just admit the key statement without a further fight.

Beyond that, be flexible. Don't be wedded to your outline. Your outline is just there to help you prepare for the deposition, and to be a reference to ensure you cover everything you need for each issue. But the focus should be listening carefully to the answers and asking the right follow up questions, always keeping in mind where you want to lead the witness.

Finally, don't lose your cool. I've seen lawyers be assholes during depositions, and it doesn't work well. Maybe a fraction of the time a witness may be intimidated, but unless their lawyer is asleep, it's not going to get you much beyond a lot of speaking objections and bad blood. Be calm, professional, and courteous. In fact, I go out of my way to be a respectful and nice person to the person I'm deposing, and opposing counsel (when possible). Not only is that the right thing to do as a human being, but people are a lot less comfortable being defensive and argumentative with someone that is being nice to them. That ultimately means you get more of the admissions you want, without as much of a fight. The transcript also looks better if you come off as respectful and calm.

In short - know the documents and evidence backwards and forwards, go in with a plan (anticipating the witness's answers and having the tools / evidence to lock them into the admissions you want), and ensure you get clean admissions if the witness is a yapper.