Before installing the SQL Server, check the system requirements for the specific SQL Server edition at https://msdn.microsoft.com/en-us/library/ms143506(v=sql.120).aspx.
Ensure the existing SQL Server supports updates. For a list of supported upgrade scenarios, see https://msdn.microsoft.com/en-us/library/ms143393(v=sql.120).aspx.
Note: Back up all your databases.
Note: You have to change the Compatibility level for every company database.
For optimal performance, it is important to update the indexes and statistics. To create these optimization jobs, you can use the ESI tool. For more information, see Exact System Information (ESI) help file.