Remove duplicate rows and order by number of occurences

Hello.

I'm trying to SELECT from the following table:

 file_id
---------
       1
       1
       2
       3
       5
       6
       9
       9
       9
      10
      10

The result I'm trying to achieve is essentially to order the
file_id column, in descending order, by the number of times
each row occurs with a given value. I would also like to remove
duplicate rows. In other words, the above table becomes
(approximately):

 file_id
---------
       9
      10
       1
       6
       5
       3
       2

The order of the last four values isn't significant (they occur
an equal number of times).

I thought that this might be the solution:

  SELECT file_id FROM temp_tagged;
    GROUP BY file_id
    ORDER BY count (file_id) DESC;

But apparently, it isn't.

Any help would be appreciated.