In principle, decision making “structure” consists of things like rules, agendas, mandates, and plans; and when these things frame our choices it frees us to focus on the substance of our work. A third-grade teacher once explained that when she decides where the kids are to sit in the classroom this does not take away their freedom, but actually frees them from the burden of having to decide this for themselves (a potentially large burden for a third-grader). It frees them to focus on math, history, and writing rather than who to sit next to.
Establishing a firm structure allows maximum creativity within the structure. Knowing there is a “container” provides safety and encourages risk-taking. Lack of structure fosters anxiety and encourages caution. Lack of structure causes inefficiency; it requires a group to go over the same ground over and over again.
Practical Tip: Establish decision making rules in your group and make it someone's responsibility to enforce them; this frees everyone else from having to worry about that. Make sure everyone understands and agrees to the rules before you decide other things. When you have a complex decision ahead of your group, break it into pieces with a timeline for deciding each piece. Focus on one piece at a time. As you near decisions, narrow choices to a small number of alternatives. Be bold in enforcing your structure...and go wild within it.