Recommended SQL server service accounts
The MSDN Page Configure Windows Service Accounts and Permissions has some detailed recommendations for the SQL Server 2014 service accounts.

The subheading for configuring the services is at Service Permissions

This is quite a detailed outline of recommendations for the SQL Server Service Accounts.  These are good recommendations, however you can make your own decisions on configuration, based on your needs for security and for being able to manage the configuration.

Truth in reading: Although we use many of these settings, we also have some variations that suit us.