The war between usability and design is not a new one. These two elements have always been pitted against one another, turning great ideas into either successes or failures (depending on the balance of power).

This battle used to be waged between engineering and industrial design, where tactile implications could mean the difference between solvency and bankruptcy. The players back then were a select few, and access to the tools and knowledge needed to create these products were few and far between.

In recent years, this conflict has moved to a new arena: our computers. Thanks to the proliferation of PCs, laptops, video game consoles and mobile devices, the conflict between usability and design has never played out over as vast a battlefield.

What’s more, most of the old barriers have been removed. Whether through desktop publishing, video editing or website creation, more and more people have access to the tools needed for creation.

But do they have the knowledge? Usability and design are two edges of the same sword, and it’s important to know how to apply principles of both to achieve the desired goal. In other words, you need to be able to discern the right information before you can use it to design an effective user interface. I've found these tenets to be particularly useful:  

• Consider the audience. Who will be using it? What are their skill sets? Their expectations? Their wants, needs and limitations? An exploratory e-learning application targeting middle-schoolers can, and should, differ greatly from an informative microsite aimed at mature adults. Different audiences have different experience levels, learning curves and learned means of interaction.
• Design with consistency in mind. By making things that act alike look alike, designers can help users learn how to successfully interact with the media. The inverse of this is also true: things that look alike should act alike. Maintaining a consistent visual design scheme is crucial for the creation of an intuitive user experience.
• Don’t forget about discriminability. Just as things that act alike should look alike, things that act differently should look different. Coincidental similarities can cause confusion, so designers should make functional elements discernible based on their behavior. Consistency and discriminability work together to help create a pleasing visual design that intuitively communicates its functional purpose.
• Utilize use-case scenarios. Early on, when an interactive piece is still just a series of static comps, use-case scenarios come in handy. Whether launching a pop-up window or filling out an opt-in form for a mailing list, it’s important to think through each step — and how the user and application will respond. This can bring to light issues that aren’t addressed in static comps, reducing the need to backtrack later on.
• Engage in usability testing. This is an invaluable stage in the creation of interactive media. Usability testing involves direct observation of how real users use the interactive media. These tests measure how well subjects respond in four key areas: accuracy, efficiency, recall and emotional responses. Changes can then be made based upon these results and re-evaluated, using the initial testing results as a baseline.
  

These are just a few of the principles that can be employed to help ensure usability in the design of interactive media. Be it your BlackBerry, laptop or PlayStation 3, in the end everyone benefits from designs that are both visually pleasing and usable.