Q: I administer 50 phones. Looking for best practices concerning iCloud. This program and my users have made it difficult to reuse phones when persons are terminated.

Several times I have had to chase after terminated employees for iCloud accounts and passwords. It has been a nightmare. How do I remove iCloud accounts from company devices, or better yet, prevent users from creating personal icloud accounts?  What are the 'best practices' concerning the use of iCloud?