A comprehensive, current guide to registering a trademark or service mark on the USPTO's Principal Register, written for founders, in-house teams, and the lawyers who advise them. It walks each decision that quietly decides an application's fate—register selection, filing basis under Sections 1(a), 1(b), 44, and 66(a), goods-and-services identification and Nice classification, standard-character versus special-form drawings, and specimens that survive examination—and explains the USPTO's January 18, 2025 fee overhaul that replaced TEAS Plus and TEAS Standard with a single base application plus surcharges. It covers examination and the DuPont likelihood-of-confusion refusal, the three-month response clock, publication and opposition before the TTAB, the Statement of Use, and post-registration maintenance under Sections 8, 9, and 15, all illustrated with a running hypothetical. Educational, not legal advice; confirm current fees at USPTO.gov.