Google Plus

• Open https://console.developers.google.com/project
• Create New Project
• Open APIs in left menu
• Find Google+ API and enable it
• Open Credentials in left menu
• Click Create New Client ID
• Select INSTALLED APPLICATION -> Android
• Enter your package name
• To obtain SHA1 go to your console and enter:

keytool -exportcert -alias androiddebugkey -keystore path-to-debug-or-production-keystore -list -v

More Info: https://developers.google.com/console/help/new/#installedapplications

Important: Make sure you've updated your details on the Consent Screen in your project settings in the Google Developer console. You need to confirm your (developer) email address, and provide a name for your app which will be displayed to the user in the permissions confirmation screen.