Product design requires creativity, experience and, if you are going to be building the product yourself, a substantial amount of technical know how.
The process of product design starts with the need of a full understanding of the requirements. Requirements gathering is a very distinct skill - sometimes the customer has a great idea, but it takes experience to know how it can be improved, tweaked and slightly changed to make it even better. Very occasionally, it is the job of the product designer to let the customer know that the idea they have just won't work. again, this ability comes with skill, judgement and experience and can save the company vast amounts of money!
Product design could be as simple as updating an existing product to make it better, or starting from scratch on a completely novel idea which exists only in someones mind. These are often distinct roles and not the same skill set. A good example of product improvement would be Dyson's bagless vacuum cleaner - a massive improvement on a product that had been around for decades before in the same form.
The steps in product development are as follows:
Specification - a detailed and thorough understanding of what the customer requires, and exactly what will be done. All details need to be thought about.
Clarification - based on the specification, it is always a good idea to change the scope at this stage if required, for example based on budget or deadline constraints.
Agreement or signoff - it is vital to get signoff of the specification and the scope of the project to ensure all parties know exactly what is required.
Patent review - with new product development, once the product has been specified, a thorough patent search is required to ensure that no other patents will be infringed. It may also be appropriate to file your own patent to protect the new idea.
A development plan is then required, detailing the exact steps and deadlines that will be worked to.
Once all of these planning stages have been taken care of and signoff has been given, the actual product development can commence.
It is always worthwhile working very closely with the customer and letting them see exactly how the work is going so there are no surprises at the end of the project - the work can be tweaked as you go along.
A prototype will be produced early on in the product design and development phase and again, this should be used as the basis for further discussions and possibly even commence user testing, depending upon the type of product, prototype produced.
At some stage the product design will be complete and the product will be made. Sign off is required to draw a line under the product development.
After sign off of the development stage, the product can go into production and in terms of the product design, the cycle starts again to ensure that the development of the product is a continuous cycle of improvement.