become

Great packaged installer for Postgres.   http://www.postgresqlformac.com/

ALSO

Edit Global Bash ProfileYou need to edit the global bash profile as follows:

1. Open the Terminal application.
2. Type sudo pico /etc/profile
3. You will be prompted to enter your password.
4. Add the following text to the end of the file:

   export PATH=/Library/PostgreSQL8/bin:$PATHexport PGDATA=/Library/PostgreSQL8/dataPostgreSQL8 in the above text might be something different depending on the version you installed. Check on your computer in the HardDrive/Library/ folder to verify the name of your installed PostgreSQL folder.

5. Press Ctrl+x to Exit. Press y to save the changes. Press the Return key to save the file.

Copied from: http://www.studiotips.net/docs/tips_sql/postgresql/installingpostgresqlonmac.html