...
    //Creating an instance of some service that your app relays on,
    //Twitter, Facebook, Google, etc
    //This service costs money to use
    return new ExpensiveServiceThatMyAppUses.Builder()
                        .initWithKey("s3cr3t_k3y_f0r_hackz0rz"); // DON'T HARDCODE THE VALUE
                        .someConfig(true)
                        .build();

...
    //AndroidManifest.xml

    //We want to use google maps in our app
    <meta-data
    android:name="com.google.android.geo.API_KEY"
    android:value="kx23x234x4x234kjfd9845n" /> // DON'T HARDCODE THE VALUE