Your first step before you make an invention submission is always to get yourself a patent. Contact a patent lawyer and the United States Patent and Trademark office. The patent lawyer will help you from the submission process which help insure that you will be legally shielded from any potential problems. There exists a fee, consider this can change, it's always best to contact the USPTO yourself. This step protects your invention and idea from getting stolen.
The next step is to find a listing of companies who accept invention submissions. As an example, in case your invention is because of cars, then find an auto-related company that's available to reviewing invention submissions. Most of these companies suggest that you patent your idea first. This protects you and prevents problems such as idea theft from occurring. You can look on the Internet for potential companies, or call businesses that interest you and ask when they review patented inventions.
A great choice for a big company. A great idea can help increase their profits. They might currently have the idea, however you got the patent before they did. This makes a partnership worth considering. They've the means and you have the idea. Just be sure they compensate you adequately.
So, when you have an invention, think about making invention submissions to relevant companies. This could assist in your own personal profits and removes from the assembly process. Make absolutely certain to patent your idea before you share your invention with a company.