Test your idea by using a simple no frills prototype(s)
The goal here is to get your product out in front of people and get valuable feedback quickly. Your first prototype should be inexpensive and simple with only core features, keep the bells and whistles at bay. Keeping things simple and not adding features until those features are absolutely necessary will save you development time, less design clutter, testing, documentation and debugging. This also means letting go, build the basics and as people use it, you’ll discover two things. First, you’ll find out where the value is. Second, you’ll find out what’s missing. Then you iterate.
Handling a product raises questions about usability, materials, form, and interactivity that would never come to someone’s mind from looking at a rendering, no matter how well it’s done. Either through user feedback or through testing, prototypes often expose weak points. From a design standpoint this helps you perfect your product, and from a funding standpoint, revealing weaknesses can help investors understand what further resources are needed.
Test this prototype out. Handle the product, is it usable, is the material right? How is the shape? Does it work like you thought, can you improve on it quickly, show other people how it works and let them try it. This is viable stuff, somethings that you could never uncover from a rendering. Listen to what they say and look at how they use the product. What do they think, do they love your product, like it, dislike it? You are looking for a sign that you’re on to something, and then you can find ways to expand from there. This process is about finding and sharing with people who will eventually want to buy your product. From a design perspective this helps you develop your product.
To develop products you have to believe that there is always a better way of doing something. And, you can't expect to get it exactly right the first time. Every iteration can be improved upon, and each of these failures teaches you something that you can apply to the next iteration. It's highly frustrating, of course, but worth it. "James Dyson"
Don't be afraid to break the prototype(s). This is the time to fail fast and to learn from prototype iterations until you have solved the problem. Once this is done, lock the design for now!
Successful product developer entrepreneurs know that the power of prototypes is for proof of concept, feedback, customer engagement and readying you for manufacturing, by forcing you to address on a small scale many of the details that will eventually come up at the factory.
Will this idea be a hit! Not every product that you develop will be. You may need to kill a product altogether and start over. Scrapping a project and starting over, even if a great deal of money, time and energy has already been spent is part of the game you have chosen!