I suggest this 3 step approach when setting up a new PMO or developing an existing one:

  1. What is the starting point? Find out about the context, i.e. Organizational structure and culture; and PM maturity (use any maturity model)
  2. What are the expectations? Ask people (PMs, functional managers, execs, etc) what help they need. Do interviews or surveys.
  3. Focus on real needs and balance. Create a plan to design a PMO that focuses on what is has been asked, not what the theory says. Ensure PMO responsibilities fit with the available tools, skillsets, processes and structure -or adjust for balance.