This guide works through the conflicts system in the order a practitioner encounters it. It covers identifying the client, the current-client rule and its consentability limits, the former-client rule and the substantial relationship test, imputation and its exceptions, screening in practice, the prospective client rule, joint representation, advance waivers, lateral hiring, former government lawyers, outside counsel guidelines, and the separate law of disqualification motions. Each part states the rule, identifies the recurring failure mode, and gives the operational instruction. The unifying idea is that conflicts law regulates the firm as an institution rather than the lawyer as an individual, which is why the answers depend on databases, engagement letters, and access controls as much as on doctrine.