The rules that govern American lawyers are state law, not federal law, and the ABA Model Rules of Professional Conduct bind no one until a state supreme court adopts them -- a fact that shapes every question in this field. This UpLaw guide walks the entire architecture of professional responsibility: how the attorney-client relationship forms (sometimes by accident), the core duties of competence, diligence, communication, and reasonable fees, and the confidentiality obligation of Rule 1.6, which is far broader than the attorney-client privilege and is constantly confused with it. It then takes the conflict-of-interest system apart piece by piece -- current-client conflicts under Rule 1.7, the categorical prohibitions of Rule 1.8, the substantial-relationship test for former clients under Rule 1.9, imputation and screening for the migrating lawyer, and the trap that Rule 1.18 sets for the beauty-contest consultation. The guide covers the organization as client and up-the-ladder reporting under Rule 1.13 and Sarbanes-Oxley Section 307, the strict-liability world of client trust accounting under Rule 1.15, withdrawal under Rule 1.16, candor to the tribunal and the client-perjury problem after Nix v. Whiteside, the no-contact rule, advertising and solicitation after Bates, unauthorized and multijurisdictional practice, supervisory duties over lawyers and nonlawyers including AI tools, and the duty to report misconduct. It closes by separating the three systems that punish lawyers -- discipline, malpractice, and disqualification -- which operate on different standards and different timelines and are routinely conflated. A running hypothetical about a firm called Harlow & Reese carries the doctrine from intake to sanction.