1. Tell them the basic rules (tell truth, answer the question asked, don't volunteer, think first talk second, listen for objections, ask for clarification if not clear, the deponent has all the real control over pace not the lawyers, ead the documents and not just the lines you're pointed to, etc.)

2. Teach the case themes (safety zones for when you don't know how to answer)

3. Go through "hot" docs they'll potbelly be asked about

4. Mock cross and critique

5. Repeat 2-5 until they stop getting better

If the witness is very good, this can take 90 minutes or less depending on the case.

Experts are different, 30b6 witnesses are different (usually some advance phone calls to gather information from other employees, and prep for trial or hearing is also different.

(http://www.autoadmit.com/thread.php?thread_id=4595658&forum_id=2#40691044)

Prepping a centrally important witness like the client (in a plaintiff's case, say) is more akin to trial prep of a centrally important witness, in that you've got to get into the witness's likeability and natural credibility. This is as much a social-skills thing as anything, but a trick I lean on heavily is preempting bad conduct that I'm worried about this particular witness exhibiting by talking about it in "general" terms (i.e., not in response to anything the witness did, so the witness doesn't feel attacked) but that are still as specific as possible -- like, give a hypothetical question and then mock and deride the shitty answer that you just *know* this witness would naturally be inclined to give. I will sometimes fabricate fake war stories about how I got rocked in a past case when, e.g., a woman I represented bickered with opposing counsel about proper terminology, refusing to accept OC's perfectly neutral terms and insisting on her own ridiculously partisan terms (on topics that are in fair dispute), pissing the jury off in the process. (This is a relatively common thing that 'karen'-type corporate witnesses will do.) With low-IQ witnesses, it's especially important that you instill in them some of the basic ways that speakers reinforce their own credibility (candid and uncaveated concessions, voluntary but not excessive qualifications regarding degrees of uncertainty, etc.). Some of the hardest witnesses are family in a wrongful-death case, since you want to prep them on content and give them some *slight* pointers on style (and excise any really problematic tendencies they might have), but you don't want to ever risk reducing the 'rawness' of their testimony by overprepping.

30(b)(6) prep is a whole different animal, irreducibly bespoke (I'm assuming we're talking for a party here, not a subpoena 30(b)(6)), and both the substance and the likeability factors are incredibly important. I'll tell you one of the most important observations I've ever had from practice: in every wrongful death / personal injury case I've ever been a part of that settled for big bucks (these were cases that were worked very, very well by a top firm), mock juries were consistently MORE DISGUSTED BY AND GAVE LOWER LIKEABILITY RATINGS to the fucking 30(b)(6) designee than to the actual individual bad actor, e.g., if you do things right, the bumbling dipshit with a bad safety record and an alcohol-abuse history that may or may not have contributed to his negligence in accidentally dropping an 13.8K-volt electrical line onto a toddler, will score higher on mock-jury ratings than the heartless, officious, stone-cold cunt that ELECTROCORP decided to make its 30(b)(6) designee because "well peggy's really organized and knows about these topics and she's very loyal to the company." (This brings up another point, which is that people often pick shitty-as-fuck 30(b)(6) designees, apparently outsourcing this function entirely to the client to pick the person who knows about the topics.)

(http://www.autoadmit.com/thread.php?thread_id=4595658&forum_id=2#40691106)