About the tip "Never leave the default database set to the master database."...

I get where you are coming from; accidentally executing something in master is not fun.

BUT also know this: if your default database is not available (offline, corrupt, restoring, etc), you will not be able to log onto the server. AT ALL.

This includes sysadmins (though the DAC can still be used).

Master will always be there (or if it's not, neither is anything else!).