There’s a very good article on Apple’ website
(http://developer.apple.com/internet/ope … tgres.html)
describing for how to install and configure PostgreSQL on Mac OS X however as an addendum
It does not describe how to startup (and shutdown) the database automatically but this page explains those steps in detail.
http://www.veenbeest.nl/technicalhints/ … acosx.html
Marc Liyanage also created a startup item to run PostgreSQL as installed by his package installer which could probably be easily adapted to deal with other installers.
http://www.entropy.ch/software/macosx/postgresql/
Hope this helps