Facebook

• Open https://developers.facebook.com/
• On the top click on Apps and register as developer
• Then click Create a New App
• Select Dashboard in the left menu
• You should see your App ID, enter it in your AndroidManifest.xml

<application>

        <meta-data
            android:name="com.facebook.sdk.ApplicationId"
            android:value="**App ID**"
        />

</application>

• Go to the Settings in left menu
• Enter your Contact Email
• Click + Add Platform
• Select Android
• Enter your package name
• To obtain key hash, use the 'keytool':

keytool -exportcert -alias <RELEASE_KEY_ALIAS> -keystore <RELEASE_KEY_PATH> | openssl sha1 -binary | openssl base64

• Go to Status & Review and make app live

More info: https://developers.facebook.com/docs/android/getting-started/