A startup is, in legal terms, a stack of documents, and how well that stack is assembled early usually decides whether a later fundraise closes cleanly or grinds to a halt in diligence. This guide works through the stack layer by layer: the formation and governance papers that create the entity and its liability shield; the founder documents that fix who owns the equity and the intellectual property, including the unforgiving thirty-day 83(b) election and its link to the qualified-small-business-stock exclusion under Section 1202; the equity engine of cap tables, option plans, and 409A valuations; the fundraising instruments from SAFEs and convertible notes to the priced-round NVCA suite; and the commercial and employment agreements that protect the operating business. For each document we explain what it does, the statutory or case-law authority behind it, when a founder actually needs it, and the specific mistakes that turn a routine form into an expensive problem. Invented worked examples built around a hypothetical company, Pallas Systems, Inc., keep the doctrine concrete. The aim is not to replace counsel but to make founders sharper clients who know what to ask for and why.