This whitepaper from the Esri Patterns and Practices team, presents some implementation guidelines in the form of a conceptual reference architecture diagram and associated best practice briefs. Organizations can use these guidelines to maximize the value of their ArcGIS implementation and meet their organizational objectives.
EDIT: This whitepaper has been updated February 2018
EDIT 2: This whitepaper has been updated May 2018.
EDIT 3: This whitepaper has been updated Dec 2018.