Don't allow agreement to be made without your input. Only agree when you intend to support and keep the agreement. Consensus over goals and consensus over means to achieve goals are different. Doing goals first is very important but groups often move to solutions before goals. People change at different rates, so be sure to accept resistance to change.
Some people are slow to move toward consensus because they consider things very deliberately.
The person who needs to hear a lot and needs time to decide may be your biggest supporter. People who change quickly sometimes keep changing. Consensus means that everyone has veto power. People who worry that consensus slows down decision making have probably witnessed it in a contentious or political forum where people have hidden agendas. In a team environment, when someone uses their veto, they are responsible for stating under what condition they would agree to the proposal.