Here are some of the things to watch out for when doing a prototype. Each is a perturbation that can disrupt the R plan to some, usually unwelcome, extent. These are mostly management issues and, for the most part, can be controlled to fit the R constraints.

• Be sure to properly set and manage the expectations of the prototype stakeholders. Comments such as: "Is it done now?" - "Is that it?" - "I didn't know it would cost this much!" - can upset a development process, especially if made by a product manager, CEO or potential customer. Stakeholders must always be aware of the intent and goals of a prototype. Early prototypes are very vulnerable to uninformed stakeholders' misuse.
• Develop product requirements as best as possible, as early as possible from:
  • Markets
  • Users / customers
  • Regulatory, Industrial and technical standards groups
  • Corporate edicts
• Failure to manage the usual inflow of user, market and testing changes to product requirements during the prototype process can drastically alter a product and project, thus R.
• Failure to establish realistic goals often creates an open-ended effort and can easily blow a PD project or a potential product's vitality.
• Be sure that what is to be prototyped can be. Something that is difficult to prototype, such as large enterprise software systems, military ordnances, space programs, etc. will need to be done in stages and not all at once. Almost anything can be prototyped to the extent that goals, interfaces, features and performance can be well defined.
• Use of Improper tools will make prototyping difficult. The prototype tools must enhance the process to fit the goals, R and stakeholder uses.
• Ensure that the intended uses of a prototype are well thought out; e.g. if it is to travel to various demo locations, it must also be designed for heavy handling, shipping and easy repair - with an adequate supply of spare parts on hand.