Corporate action taken without observing the required formalities can be voided, which matters most when the parties later disagree about whether something was approved.
Notice. Statutes and bylaws set the period and the required content. A special meeting notice usually must state the purpose, and business outside it cannot be transacted. Defective notice is curable by waiver, in writing or by attendance without objection.
Quorum is measured against shares entitled to vote, at the threshold set by the bylaws subject to statutory minimums. Once established, whether it can be broken by departure varies.
Voting standards. A plurality for directors, a majority of votes cast for most other matters, and higher thresholds for fundamental changes. The difference between a majority of shares outstanding and a majority of votes cast decides close questions and is frequently misread.
Written consent in lieu of a meeting is permitted, sometimes requiring unanimity and sometimes the same vote as at a meeting, with notice to non-consenting holders. Check the statute and the charter, because defaults differ.
Minutes are the record. They should show notice, quorum, the resolution as adopted, and abstentions or recusals of interested parties. Minutes written months later, in litigation, carry the weight they deserve.