You can choose any inventory management you want or use one of next examples.
One or two hosts
In most scenarios your project will have one or two hosts: one for production and one for staging. So there is no need to separate inventory file, you can write everything in single deploy.php file.
For single host you don't need anything. Deployer will deploy to all defined hosts if no stage parameter specified.
If you have one host for production and another for staging the next example is sufficient.
Right behavior for
dep deploycommand is to deploy staging, and to deploy prod is
dep deploy production.
Best practice is to leave connecting information for hosts in the
~/.ssh/configfile. That way you allow different users to connect in different ways.
Separate inventory files