This guide covers patents from invention through enforcement. It sets out the four requirements — eligible subject matter, novelty, non-obviousness, and adequate disclosure — with the decisions that define each, and explains why disclosure failures are the most common cause of a patent proving worthless. It treats claim drafting as the central craft, explains the structure of a claim, and covers claim construction as the pivotal event in any dispute. It walks through prosecution, including provisional applications, publication, office actions, and the permanent cost of narrowing amendments. It covers infringement, the doctrine of equivalents, defenses, exhaustion, marking, and venue. It treats administrative validity review as the reality it has become, and closes with remedies, ownership, portfolio strategy, and the choice between patenting and secrecy.