Before you can code anything, you need an idea, a novel or interesting concept that you believe some audience will enjoy or find useful. In the brainstorming stage, simple ideas that you can easily explain to others are important. If you come up with a concept that takes a long time to explain, or is confusing when you attempt to explain it to others, it may be time to come up with another concept, or to simplify the one on which you are working.
Once you have a concept, it is a good idea to codify it in a series of steps, which clearly lays out the game or application rules for the end user and clearly defines the objective or purpose of the application.
Idea: Klondike Solitaire.
Objective: Order a deck of 52 playing cards by suit ...