Read the documentation: https://developers.google.com/actions/
Google+ Actions on Google Developers Community: https://g.co/actionsdev
Wayne Piekarski (https://google.com/+WaynePiekarski) introduces the Google Assistant, and how to develop your own Conversation Actions to be a part of this new ecosystem. Using the Actions SDK, developers can directly parse requests and construct responses that adhere to the Conversation API. Tools such as API.AI make this developer experience even easier, using a graphical user interface to define the conversation. This video gives a simple overview of the concepts and steps needed for a developer to get started building their own Conversations Actions.