How to deal with order by, group by, distinct for user-defined types

Hi,

I implemented a user-defined type, say X, and when I want to do the
following queries, Postgresql will complain

CREATE TABLE Table1 ( id integer, object X );

SELECT X, count(*) from Table1
GROUP BY X;

> ERROR: could not identify an ordering operator for type X
> HINT: Use an explicit ordering operator or modify the query.

My question is: how do I find or define ordering operators for my
user-defined type?

Thanks.

Ruey-Lung Hsiao