You might end up with something like: Capable of handling gifs, jpegs and bitmap images.
Easy, one-click picture editing.
Simple to use, fast to learn...
And so on...
I usually find that this is the most enjoyable part of the whole project. As you come to think of each little feature, you’ll find that you actually get quite excited. The project will begin to form in your mind and each feature should lead naturally onto the next.

User Stories
Here we get into more detail. User stories describe the program from the user’s perspective. For the programmer these are the best way to understand precisely what your program is expected to do. For example, you might have a user story that ran like this:
“User right-clicks on image and receives a menu offering Edit functions. The user can then effect a change to the whole image by clicking on one of the options.”
The user story has to be clear enough to be easily understood by the programmer but detailed enough to provide guidance. You want the programmer to be able to look at it and say, “Hey, that’s cool!”

Data Directory
This is where things get complicated. Most software programs work at some level by storing and retrieving data. If you don’t put the right data in the right place, you’re going to get the wrong results, bugs and delays. Personally, I leave this part to the programmer. If he can’t get it right, what chance do I have?