Program for creating plan for complex android applications

Maybe that is not the right question for this stack and I am willing to delete it if you want me to. I just have no idea where else should I post it if not here.

I am looking for a program used for creating application plan. Something like writing down application features, designing them and other preparations needed in order to start developing the app.

I am not sure how to make this question more specific to fit to this community. Maybe by asking what preparations are needed in order to do good complex application for android? It can be very general since there are most likely many tasks to do before actual development starts.

Any edit suggestions are welcome.