After running the installer that you can find here: http://www.postgresql.org/download/macosx
- Switch to root ( su - ).
- Then su - postgresql (the installer creates a postgresql user on your box, but you can't login directly as that user, except through root since su - as root bypasses password checks).
- Go to your bin directory for PostgreSQL (default on OSX through the install wizard is /Library/PostgreSQL/9.0/bin) and run ./createdb -s -P yourusername (I used my default OSX user). It will prompt you for a password that you want to use for this user. I used my default OSX user's password. One less thing to remember.
- Exit back to your default user.
- In your .bash_profile, add this to your PATH variable :/Library/PostgreSQL/9.0/bin (change this if you installed to some other directory).
- Be sure to run a source ~/.bash_profile so this variable takes effect in your current terminal session.
Now your default OSX user can run PostgreSQL commands.