Particularly in today's tough environment, lack of leadership will spell failure probably more quickly than any other deficiency. Firm governance and management. A law firm, just as any other business, will not run itself. There must be a formal governance structure. There is no magic way to do it.
Different things work for different groups at different stages of firm growth and evolution.
It goes without saying that the bigger you get, the more structure you need. Whatever structure the group decides upon will impact the culture. The partnership agreement has to come first. Lawyers sometimes postpone executing an agreement because they can't agree on content. One thing is certain.