Today Apps vary from so many categories to another. You can easily find an App for every need and occasion. However, once you've found your perfect app, you start to notice some lacks and places for improvement. You write feedback and wait for modifications, but you begin to feel impatient. Why don't you stop the wait and create the app yourself? Creating a new app similar to a previous one is not forbidden - it is the core of competition within the world of Apps. You don't have to wait for them to make your ideal app - you go and create it yourself.
First, you have to know what you want. And for this step, all you need is paper and a pen. Dream, reach, and go for something. Create a framework for your idea and write down your answers on what you want to achieve with your app and what problem/problems you want it to solve. Write it all on paper and make them a reality. Are they possible to reach?
Once your answers and goals start to appear more clearly, you go to your toolbox and get the most essential tool, brainstorming. Brainstorm through every single aspect of your idea. The designs. The colors. The features. The price. Compare to other Apps. If possible, read some feedback they have received. Scroll through App Store, learn, learn, and learn, try, try, and try. These different ways and alternatives towards your goal that brainstorming creates are essential to keep as Plan b's and c's. If you are prepared for a failure of one way, you have another way to try right there and ready to go.
You don't have to get technical with this step, just let loose and set your imagination free. However, don't forget to put time and effort into doing research. You need something for comparison and to set you an example. As mentioned earlier, see what other Apps have done and how people have responded. Use your own experiences, ask your friends and family. What would they do better? That way, you learn how YOU want to make this App work.