The following are elements of a good design methodology:
Create a team of individuals who specialize in development, visual design, writing and human factors. It is a rare individual who can wear all hats equally well.
There is a process for designing effect UIs which facilitates designing the best possible interface in the most cost-effective manner.
During the design phase of your project, you will be laying the foundation for a usable interface. In this part of the process, you define the objectives and features for your product, understand who your users are and their tasks, intentions, and goals. You will begin defining your conceptual framework or design model to represent your product with the knowledge and experience of your target audience. Write up your design as a general specification. This will help make the design more concrete and reveal issues and gaps.
Once you define a design model, prototype some of the basic aspects of the design. Use ``paper-and-pencil'' models to start since it is fast and easy to change. Prototypes provide an effective tool for communicating the design. They also help to define task flow and to better visualize the design. You can also get low-cost user input on the design with prototypes which is particularly useful early in the design process.
When you have a prototype, get users involved. Usability testing a design provides very valuable information and is a key part of the success of a product. Testing provides you with task efficiency and success or failure data and can provide information about users' perceptions, satisfaction, questions, and problems. Use test participants that fit your profile of your target audience.
In addition to usability testing, you will want to perform
usability assessments. These take many forms, including but
not limited to, walkthroughs, focus groups, and heuristic
evaluations. The more information
about how your users will work with the product that you
get, and the earlier that you get it, the more effective
your UI will be for your users.
Because it is inevitable that testing will uncover the weaknesses of a design and most likely provide additional information you will want to use, you begin the entire design process again. Take what you have learned and refine the design, re-prototype and retest. This iteration should continue through the development process until you are satisfied with the overall result.