We can find many texts on the internet about principles of designing the user interface. I will mention ten basic principles in the design.
1. Know your users
This means that before the creation of the application we should specify a target user group for which we are creating our application. Consequently, we will create our own user interface depending on whether if it is about children or adults with some basic knowledge. A good example in designing the user interface is for example ATM machine. Most people came to the ATM to pick up money. If the ATM machine first paid off the money and then your card, probably we will forget to take the card. For this reason, the ATM machine first returns a card and then money.
2. Pay attention to patterns
Most users have opened their Facebook, Twitter, e-mail accounts and as well they read newspapers from different websites. This practically means that they are already familiar with the interface which meets there. I recommend using similar patterns when you are creating user interfaces in order to achieve for the user to feel familiar with your application.
3. Keep the consistency of User Interface
This means that before creating the user interface we should specify the font size, fonts and colors that you will use. As a first time when you inform user that he received an error message in red letters, he will expect every time he sees red letters that he had made a mistake.
4. Use visual hierarchy
The first look which is in the focus of the user is what is the most important. On this way you will enable the reduction of complex content that will also look very simple.
5. Provide feedback
The user always expects to receive a feedback, whether if it is done something properly or he made a mistake. The feedback means that if you expect from the user to enter a date, for example, then emphasize which form of the date you expect or if user entered decimal numbers decide do you expect to enter it with point or decimal comma.
6. Tolerance for mistakes
No matter how much your application looks extremely simple to use, remember that the user will make intentional or unintentional mistakes. It is necessary to ensure that the program will not "break" in this case and to clearly indicate that the error occurred.
7. Encourage your customers
Users who have already become familiar with your application will expect to get the possibility to use some shortcuts. It is needed to provide it.
8. Speak their language
Everything that is on your application, whether they are some error messages or any other text related to your application always use a simple and understandable language. No one will not be impressed to receive message box with an incomprehensible message that leads to depress the user.
9. Keep it simple
This implies that the best interface, invisible interface is to enable the user a maximum focus on for what your application was designed. For example, no one will notice that is comfortable in the room while air conditioner works but if it is hot in the room, everyone will notice that air conditioner does not work.
10. Continue to move forward
This is a very significant principle. In fact, if you are a beginner you will often make the proper mistakes. Learn from your colleagues and from the mistakes and eventually you will make a decent and nice user interface.