By default, the current directory is used, but the --path option allows you to set a specific path that you can use instead. For example, this will work from any directory:
$ ~/odoo-dev/odoo/odoo-bin start --path=~/odoo-dev/my-odoo
The database to use can also be overridden using the usual -d option. In fact, all of the other usual odoo-bin command-line arguments will work, except --addons-path. For example, to set the server listening port, use the following command:
$ ../odoo/odoo-bin start -p 8080 -i base
As we can see, the Odoo start command can be a convenient way to quick-start Odoo instances with their own module directory.