Good design is...
efficient.
If we break this concept down and examine its core elements we find that it yields an array of attributes. From this we can derive that efficiency gives us 10 principles for good design. Good design must be:
Useful
A useful design is an efficient design and efficient design is useful. It must accomplish utility through its function which is its purpose. Aesthetic and psychological aspects may aid in the usefulness of a product, however superfluous and erroneous elements should be eliminated to maximize utility and thus efficiency.
Lasting
Good design is lasting. Lasting design is efficient. Efficiency can be seen in longevity. As technology alters our lifestyle and time passes a product must be able to hold its own or adapt to change. It must adapt by means of scalability and modularity, through augmentation and calculated adaptations. Lasting design is efficient because having to buy a new product or redesign in a short period of time is inefficient and costly.
Green
Good design is green. Efficiency lends itself to being environmentally friendly. Utilizing minimal resources and extracting the maximum potential from those resources keeps waste to a minimum. This must be true during the lifetime of the product as well as in its aftermath. Getting more from less in design is essential and must always be strived for.
Simple
Good design yields simplicity. Getting more from less is efficient. Thus, less is more. Everything that a product isn't is what it is. Ridding an object from extraneous and cumbersome elements frees it to perform efficiently, mitigates complexity, and reduces potential problems. Weather additive or subtractive methods are used in development, the less complex a system the greater chance it has to function as intended for a prolonged period of time without problems or failure. Simple is better. "An object should only be as simple as it needs to be, but no simpler" - Albert Einstein
Aesthetic
Beauty is in the eye of the beholder. We believe that efficient design is beautiful because it pleases and delights us. It is beautiful because it rids the item of the superfluous and only leaves the essential. Efficiency is beautiful, because the product's design and aesthetics flow from the function and not the other way around. However, it should be pointed out that psychological aspects play an important role and cannot be disregarded. Therefore a product must have just the right amount of calculated beauty dependent upon the intended purpose. For example, a wrench can only have so many aesthetic elements before it becomes cumbersome, inefficient, and ultimately useless to the user. An appropriate balance must be struck.
Innovative
Efficient design is innovative. New ideas come about from a need to fill a void, solve a problem, maximize productivity, or reduce waste. Any or all of these situations are solved through the design process. New technology is never ending. Therefore both product and design must be on par with developing and emerging technologies. If we design the product parallel to the technology, the product will be pushed by the technology and the technology by the product. For example, cell phones were produced because of new technology and new technologies had to be invented to solve new problems that cell phones faced.
Intelligible
Time and effort are wasted in trying to discern what an object's function is if it is not clear. Therefore it is wasteful and thus inefficient. Good design is Intelligible. For a design to be efficient one must be able to quickly understand its function and use. If it is obscure or incomprehensible it is wasteful, inefficient, and useless. An intelligible object presents its purpose and function, simply, quickly, and clearly. Thus the user knows what to do with it in a timely and efficient manner. A well designed product should be no less than self-explanatory and should try to aid the user as much as possible without obstructing functionality or distracting the user.
Unobtrusive
Efficiency makes a product no more and no less than what its function is. Therefore it does not get in the way of fulfilling its purpose or the user's objectives, rather it aids in doing so. Good design calls for a product that does not intrude upon the function of itself or others in its environment. This is especially evident in more complex systems or in environments where products interact or come into contact with each other.
Thorough
Good design is thorough. It's all in the details. In producing an efficient design meticulous attention, even to the most minute of details, is essential. Efficiency is thoroughly thought out and crafted by small refinements and careful calculations. It does not come from chance, rather calculated efforts based on research, knowledge, and experience. The product must come together in such a way that specific methods are applied in an exact order to produce a specifically desired result.
Honest
Good design is honest. Honest design is efficient. It is efficient because an honest product does not deceive the user into thinking that it can perform functions other than those which it was meant to fulfill. Furthermore, an honest product is built to perform specific tasks under daily use and is designed to hold up to certain criteria. These criteria should in no way mislead the user. For example: A concrete hammer will fail almost immediately whereas a metal hammer will function as intended for an extended period of time. An honest product must be honest in all aspects, seen and unseen by the user. An honest product does not deceive by attempting to appear as more than the sum of its parts. It does not trick the user into thinking it is something more even if the user finds more use from it than originally intended.