Another obvious thing to remember, at least when installing brand new instance and not doing an in-place upgrade:
The collation settings !!
We have upgraded to SQL Server 2016 on brand new hardware at a hosting company.
We described the complete installation to them but did not specify that we did NOT want the standard Collation, but of course needed the same as all the databases were using.
Now, 3 months later, when facing some performance issues, one of our key findings is the problems with tempDB and OLTP database not having same Collation, and we are stuck with it 🙂