1. Planning Phase
Identify your objective that will achieved by the App (Your requirements)
2. Design Phase
Designing Phase, UI (user Interface design) can be start from basic wire farming technique then you can design it in Adobe Illustrator/Photoshop or Firework. Design should be much simpler as it possible, easy to use and easy to understand.
3. Development Phase
Start from basic flow-chart, write a basic algorithm and develop.
4. Testing & Reviews
After the development phase, you need to test the app, you can share with your friends or colleagues, accept their reviews, comments, suggestion and fix the error/bug. After this phase your app is ready to publish on the internet.