Many investors produce, market and sell their own inventions. In general, however, it is far easier and more profitable to sell the invention idea itself. An established company can effectively manufacture, advertise and distribute a product in a way a typical inventor cannot. License your idea to the company for a cut of the sales, or sell it off for a substantial sum of money.
Hire a patent lawyer. Enlist his services to patent your invention and draft a non-disclosure agreement. The patent will protect your invention from theft, and the nondisclosure agreement will stop potential investors from working to come up with similar devices without giving you credit.
Create a mockup of your invention. If it is something that is easy to build, create as complete a model as possible. If it is something that is beyond your ability to manufacture, create a scale model or a mockup of the parts. You can also have an outside company transform your idea into a prototype.
Come up with a presentation. Have professional pamphlets and business cards printed up. Use charts or a presentation program like PowerPoint to organize your information. Devise a short speech explaining what your product is, how it is used and why people would want it.
Meet with investors. Research groups of investors who are interested in products that are similar to yours. Travel to meet them and give a short presentation.
Negotiate your terms. Investors who are interested in a product will typically either license it or buy exclusive rights to it. If they license it, they purchase the right to manufacture it for a set period of time. If they buy it, you lose all rights forever. Usually, holding onto your rights and leasing them out for a set period is the better option. If your invention is revolutionary, however, the investors may be willing to give you enough money for a purchase to make it worth your while.
Be sure to budget. Patent attorneys' fees, airline tickets to meet investors, parts for prototypes, and assorted other expenses are going to add up to a lot of money.