Preparation is the single largest variable a lawyer controls in a deposition, and it is also the place where the ethical line is thinnest, because the same session that makes a witness clear can be used to make a witness false. This guide separates the two: it states the rule that a lawyer may prepare a witness thoroughly but may never counsel or assist false testimony, then builds a working curriculum out of that constraint, moving from process education through document review, subject-matter walkthroughs, and full mock examination. It gives sustained attention to the problems that actually defeat preparation - the witness who volunteers, the witness who guesses rather than admitting ignorance, the witness who adopts the examiner's language, and the witness who is angry - and to the discovery consequences of preparation itself under Federal Rule of Evidence 612 and the selection-and-compilation work-product doctrine. A dedicated part addresses the Rule 30(b)(6) designee, whose preparation is a corporate legal duty rather than a courtesy, and whose unprepared answers can be treated as a failure to appear. Further parts cover executives, engineers and other technical witnesses, retained experts, former employees, interpreted testimony, vulnerable witnesses, and remote preparation, and the guide closes with a mock-deposition design, a debrief protocol, working checklists, and an FAQ.