More than any other, the most often asked question of the Windows Time Service is "How do I configure w32time for high accuracy?" Bob Drake has taken the time to answer this question over at the Ask the Directory Services Team blog. You can read his post here: http://blogs.technet.com/askds/archive/2007/10/23/high-accuracy-w32time-requirements.aspx
Note: We have made improvements to Windows Server 2016 to support high accuracy time. See https://aka.ms/WS2016Time for more information.