Think about the quality level of the prototype that you need.
This also depends on what you want from the people you’ll be testing with. What type of feedback are you looking for?
It’s fine to have something that is clearly just made from cardboard, people will be more open to actually give comments about what to improve. When something looks all shiny and professionally finished they assume it is right and won’t give any deeper comments than e.g. that they don’t like the color.
Make it tangible (= detectable or experienced by the senses).
It’s not a fixed choice of direction it’s a try-out.
Don’t be afraid to just make something.
It’s about getting your head and hands around the process. We are used to using either head or hands, but it’s the head-hands dialogue that works.
Go beyond words to let others understand
You can find examples of prototypes on www.perceptivequalities.com
Suitable for very complex projects. There isn’t a single right answer but there is a good solution. You can use experience prototyping to find and validate this solution.
Just start trying, making acting.
It can be helpful to make the client a part of the process, to include them. Often a client doesn’t know what they really want and being a part of the process can help. (Some clients don’t want this, to them you just present the results)