To become a user interface designer you will likely need a particular blend of educational background and prior work experience. Actually learning to design user interfaces involves a combination of different ideas and knowledge areas, from understanding human cognitive processes and behavior to learning scripting languages and graphic design programs. You can attend classes and conferences to enhance your knowledge in these areas, as well as read a number of books to learn more about designing user interfaces. Once you have done this, you should try to get some practical experience to augment your education and training, and your experience will help you become a professional user interface designer.
A user interface designer is someone who creates user interfaces, typically graphical user interfaces (GUIs) for different companies and applications. The GUI is what most users of a particular program or website will interact with during basic usage of the product. Everything from operating systems to websites utilizes a GUI to allow customers or users of the program to more easily navigate the various options and controls available through the software or website. The interface designer designs the overall concept of a GUI and works with others to create the user interface that others will interact with.
There are typically two major areas a person interested in becoming a user interface designer will need to focus on: education and experience. You can receive education from a professional institution, such as a college or technical school, as well as enhance your understanding in other ways. Many designers have a background in areas such as computer science or engineering, though many people enter user interface design with a degree in psychology or sociology. You should look for classes in human computer interaction (HCI) and usability, and read books that are foundational to understanding user interface design.
Most companies looking to hire a user interface designer also look for previous experience to actually demonstrate what a candidate knows how to do. You might look for work for small companies that cannot pay much, but would provide you with opportunities to build and grow your professional portfolio. It is often a good idea to showcase certain things in your portfolio potential employers will want to see, such as documentation, demonstrating how you developed ideas from one stage to the next, and providing examples of effective problem solving on a project. Experience can potentially be more important for a designer than a philosophical understanding of design, but you should strive to have both to make yourself more appealing than other candidates.