In their 1996 book Lean Thinking, James P. Womack and Daniel T. Jones defined a set of five basic principles that characterize a lean enterprise:

"The critical starting point for lean thinking is value. Value can only be defined by the ultimate customer. And it's only meaningful when expressed in terms of a specific product (a good or a service, and often both at once), which meets the customer's needs at a specific price at a specific time."

Above all, lean practitioners must be relentlessly focused on the customer when specifying and creating value. Neither shareholder needs, nor senior management's financial mind-set, nor political exigencies, nor any other consideration should distract from this critical first step in lean thinking.

Once more, here's another passage from Womack and Jones on how managers can start off on the wrong path:

 

 "Why is it so hard to start at the right place, to correctly define value? Partly because most producers want to make what they are already making and partly because many customers only know how to ask for some variant of what they are already getting. They simply start in the wrong place and end up at the wrong destination. Then, when providers or customers do decide to rethink value, they often fall back on simply formulas‹lower cost, increased product variety through customization, instant delivery‹rather than jointly analyzing value and challenging old definitions to see what¹s really needed."