You want to find out that this person will seek to truly understand what you are trying to accomplish with your app, and the functionality.

The following items are good to hear:

☛ Objective statement or purpose of the app for the app publisher

☛ Description of the target audience or user demographics

☛ Any existing apps that it might be similar to

☛ Wireframes

☛ Artwork; The best developers will say they require the artwork to be completed before development. This avoids delays, and helps the developer understand the look, feel and branding you are trying to achieve.