I just found where they had the list of OLD, NEW, etc., then there was an example showing how to use NEW. OLD was the second entry in section 37.10, [link|http://www.postgresql.org/docs/7.4/static/plpgsql-trigger.html|"Trigger Procedures".]

Installing the languages is right at the beginning of the [link|http://www.postgresql.org/docs/7.4/static/xplang.html|procedural language doc]:
A procedural language must be "installed" into each database where it is to be used. But procedural languages installed in the template1 database are automatically available in all subsequently created databases. So the database administrator can decide which languages are available in which databases, and can make some languages available by default if he chooses.

For the languages supplied with the standard distribution, the shell script createlang may be used instead of carrying out the details by hand. For example, to install PL/pgSQL into the template1 database, use

createlang plpgsql template1