In principle, consensus generally means that all perspectives are heard and all concerns are addressed so all participants can willingly consent to those decisions. Many groups aspire to make decisions by consensus, but very few have specific protocols in place to guide its implementation. There are no “Robert's Rules of Order” for consensus. Groups often plunge ahead resolved to use consensus but with little or no structural underpinnings.
Practical Tip: If you are going to use consensus as your official decision-making method, be specific at the outset about what it means for your group. How, specifically, will you make sure that all perspectives are heard, all concerns are addressed, and what steps will be followed when there is a “block.” Once your rules are decided, follow them with a degree of formality. Structure and protocol are just as important in consensus decision-making as they are in any other type of decision-making.
Being casual about the rules just makes a mess.