brew install postgresql
initdb /usr/local/var/postgres
cp /usr/local/Cellar/postgresql/9.3.4/homebrew.mxcl.postgresql.plist ~/Library/LaunchAgents
launchctl load -w homebrew.mxcl.postgresql.plist
The username for development is in the database.yml
createuser --pwprompt <username>
Again, see database.yml for dev database name
createdb -0<username> -Eutf8 <database_name>