Formalities protect limited liability, resolve later disputes about what was approved, and are the first thing examined in litigation.
Separate finances. Distinct bank accounts, no payment of personal expenses from company funds, documented loans between owner and company with notes and interest, and arm’s-length terms for any related-party arrangement. This matters more than any other item on the list.
Adequate capitalisation at formation relative to the business’s foreseeable obligations, and insurance appropriate to the risk.
Annual meetings or consents of directors and shareholders, or the members and managers of an LLC, with written records. Consents in lieu of meetings are fine; nothing at all is not.
Approvals for significant actions. Major contracts, borrowings, guarantees, compensation of officers, distributions, and any transaction in which a manager or director is interested — the last of these with disclosure and disinterested approval recorded.
Signing correctly. In the entity’s name, by an authorised person, with title stated. Personal signatures on company obligations create personal liability more often than any veil-piercing theory.
Registered agent and filings kept current; administrative dissolution for a missed annual report is common and creates real problems mid-transaction.
Documents that exist. An operating agreement or bylaws, actually signed, and a current ownership ledger.