Legal formalities are essential for startups to avoid costly mistakes later. When starting a venture, founders must choose a legal entity like a company, LLP, or partnership and draft key documents. These include a memorandum of association outlining the company's objectives, articles of association establishing rules and procedures, and a founders' agreement clarifying roles and equity splits if multiple founders. During fundraising, a non-binding term sheet sets the basic investment terms before legal agreements are finalized. Common mistakes include not clearly defining exit terms, misunderstanding investment documents, and failing to formalize employment agreements. It is important for founders to work closely with legal counsel well-versed in relevant laws.