Must include the specific date and time when the board met to pass the resolution. Must authorize a specific person or persons by name and title. Must include the types of contracts and agreements the specific individual or individuals can execute on behalf of the corporation.
You simply resign. Submit a written statement to the board of directors informing them of your resignation and its effective date. Resigning won't cut off anyone's right to try and sue you for wrongful acts you committed while you were an officer.