Moving Exchange database or defrag'ing Exchange database

I still see these questions asked pretty frequently:

1)  I need to defrag/compact my Exchange 2007 / 2010 / 2013 database?  What is the best way to do that? 
(or)
2)  I need to move my databases to a new disk.  What is the best way to do that?

If you have the free disk space, by and large the best way to defrag or move data is to just create a new database on the new disk.  Then, use the New-MoveRequest option to move the mailboxes over. This takes a bit longer but it also minimizes downtime and customer annoyances.  And, in the case of a defrag, it minimizes risk to the database file.