How to enable plpgsql functions (and triggers)

I wanted to use PL/pgsql to write some functions for use with
triggers, and thought others might benefit from a concise description
of how to enable this without having to scour the postgresql
documentation. This was with a default install of pgsql v6.5.2 on
RH6.0.

CREATE FUNCTION plpgsql_call_handler () RETURNS OPAQUE AS
'/usr/local/pgsql/lib/plpgsql.so' LANGUAGE 'C';

CREATE TRUSTED PROCEDURAL LANGUAGE 'plpgsql'
HANDLER plpgsql_call_handler
LANCOMPILER 'PL/pgSQL';

Ref: http://www.postgresql.org/docs/postgres/xplang.htm#XPLANG-TITLE

The trigger example at
http://www.postgresql.org/docs/postgres/xplang19094.htm does not work
without this (there's also a missing single quote after "AS").

Cheers.