Research
You need to research your product in the obvious markets it will be sold in. Being the product developer, you understand the value (it will bring in your eyes), realize and understand the markets it will be sold in, and the true market value. You should also have a patent search completed to see if your product is patentable. 
 
Design
When designing any product it is essential to know how the product will be manufactured and design the product around the manufacturing process. In other words, design it so the manufacturing process is simple and fast.
 
Engineering
Engineer your product to deliver maximum performance; in many cases the inventor may lack the engineering experience and capabilities to do so. Disclose your invention with a Non-Disclosure Non-Compete Agreement to an experienced product developer, machinist or engineer and get a written evaluation with diagrams and notes on engineering the product and the manufacturing presses. 
 
Prototyping
When building a prototype, it necessarily doses not need to be produced in the building material that the finished product will be manufactured in. The prototype does need to perform the task it is designed and engineered for and be within reasonable size of the finished product that will be sold to the public. 

US Patents and Trademarks
If you are capable of writing your own patent application, you can electronic file it for $425.00 with the United States Patent and Trademark Office (USPTO) www.uspto.gov  for all the information. 

US Copyrights
Protect your writings: publications, books, movie and television ideas, etc. with copyrights. Go to the United States Copyright Office (USCO) www.copyright.gov  for all the information. 

You can also protect your claim of priority of ownership to your script, screenplay or an idea for 10 years for $10 with the Writers Guild of America, East www.wgaeast.org.