Aim for the best combination of possible trade-offs.
For example, metal is durable but it makes a lot of noise and conducts heat easily.
Prepare a list of specific design options that are known to work.
This is the key to fast product development. For example, if you had good results with "Aluminum 6061-T651, Anodized Mil-A-8625 Type III, Dyed Sanodal Deep Black H3LW", it's easy to reuse that specification for new products with confidence.
Functional Description: Define what a product is supposed to do and assess the conditions in which those features are valuable.
For example, tables are passive platforms that hold objects higher than the floor because the human body is more comfortable looking at things closer to head height and grabbing objects closer to waist height. The functional description is useful because it clarifies the scope and rationale of the core design, setting initial constraints for the convergent development process and considering the real needs of different application environments.
Idealism: Understand the factors that make a product excellent.
Ideal properties vary across different products. Paper is ok to be extremely light-weight, whereas a laptop needs enough weight to stand firm on a table against the wind.
Possibility Frontier: Pay close attention to the timing of product development against actual production, distribution, and consumption.
Product design does not occur in a vacuum. It is bound by time, cost, technological dependencies, business needs, and other real-world constraints. Sometimes it's worth waiting for underlying technologies to improve. Consider the case where a business waits 2 years for solid state drives to mature in price and reliability before developing the next version of their industrial control electronics. If they did not wait, their new version would have been rendered somewhat obsolete (either using old spinning drives or being much more expensive) soon after launching their product. The possibility frontier is where the product development process overlaps the practical rigors of business and economics.