depends on how you have organised your Home/Splash Activity and where you have defined the heavy tasks in the Activity lifecycle callbacks.

In general, test your app and see which methods take much time than others and start with optimizing them. Try do minimum(no) work at onCreate() and onStart(). Send time consuming work to back thread.

Further you can checkout Launch Fast section of this 9Part post by Chet Haase. https://medium.com/google-developers/developing-for-android-iii-2efc140167fd#.7fkyvlowf