Examples
Set the mimetype on a file:
$ svn propset svn:mime-type image/jpeg foo.jpg
property 'svn:mime-type' set on 'foo.jpg'
On a UNIX system, if you want a file to have the executable permission set:
$ svn propset svn:executable ON somescript
property 'svn:executable' set on 'somescript'
Perhaps you have an internal policy to set certain properties for the benefit of your coworkers: