Teamwork is very difficult to teach when it comes to decision-making. Practice helps. Exercises help. Often though some essential guidelines are not used to make decisions through consensus.
Read what Bob Frisch offers as tactics "which are designed to fix the decision-making process...and have far greater success in achieving real alignment." (http://harvardbusinessonline.hbsp.harvard.edu/hbsp/hbr/articles/article.jsp?articleID=R0811J&ml_action=get-article&print=true&ml_issueid=BR0811)