Prototyping is a learning process, and you should not be afraid of making mistakes as long as you learn from them. It's perfectly fine to find unanswered questions about your design and solve them as you build your prototype. Experimentation is part of the process. A bit of planning, however, can help you to save some time.
When building your prototype, you need to take shortcuts and cut many corners to be efficient. These decisions may limit your future options, and it is good to anticipate their effects a bit. You don't want to find yourself in the middle of building a prototype and realize that the tool you chose does not support the interaction you absolutely need for a key part of your prototype.
In this section, we will provide some aspects to consider before starting your prototype. Plan a bit, but feel free to experiment as you prototype...