Discovery is the longest, most expensive, and most consequential phase of a civil case, and it is governed by a small set of rules that reward precision and punish improvisation. This guide walks through the entire process in order: the scheduling conference, initial disclosures, each written device, depositions, third-party subpoenas, and expert exchange. It treats electronically stored information as the central problem it has become, covering the preservation trigger, the litigation hold, forms of production, and the graduated spoliation framework. It explains attorney-client privilege, work product, the privilege log, clawback agreements, and protective orders, with the case law that defines each. It sets out the enforcement ladder from deficiency letter to sanctions, including the mandatory fee-shifting provision most litigants overlook. It closes with drafting templates, a deadline table, state-court variations, and answers to the questions that arise most often.