A decade after Alice Corp. v. CLS Bank, software and business-method patents still die under 35 U.S.C. § 101 at rates that unnerve inventors and their counsel, frequently on a motion to dismiss before discovery ever begins. Yet eligibility remains winnable for those who understand that the outcome turns less on what was invented than on how the claim describes it. This guide traces the Alice/Mayo two-step and its statutory and historical roots from Benson through Diehr, Bilski, and Mayo; maps the Federal Circuit precedents that mark the narrow path to eligibility (Enfish, DDR Holdings, McRO, BASCOM, Core Wireless, Finjan) against the cases where claims routinely fail (Electric Power Group, Symantec, Capital One, Broadband iTV, Recentive); and decodes the USPTO's examination machinery, including the 2019 Patent Eligibility Guidance, the 2024 AI update, and the precedential Ex parte Desjardins. It then turns to craft: claim-drafting techniques, the Berkheimer factual burden, functional-claiming pitfalls under Section 112(f), prosecution tactics, portfolio audits, and layered protection pairing patents with trade secrets, copyright, contracts, and design patents. The aim is a usable map of exactly where claims live and where they die.