Why should I file a Provisional Application for Patent?
A provisional application for patent is a great first step towards protecting your invention. It establishes an early filing date for your invention while you put the finishing touches on it, finish your non-provisional patent application, seek funding and do market research. Having a provisional application on file means that you can disclose details about your invention with everyone on notice that your invention is "Patent Pending." (You can use the "Patent Pending" label for the entire duration of your 12 month provisional period, or for the entire examination period of your non-provisional utility application.) Also, provisional applications are not published by the USPTO so as not to compromise your invention's secrecy.
Provisional applications are less expensive and easier to file than non-provisional patent applications, can be done quickly, and should be done in advance of an invention's public disclosure, although following a disclosure is fine also. Most importantly, filing a provisional application establishes an official filing date with the USPTO--and now that the PTO is moving from "First-to-Invent" to "First-Inventor-to-File," your filing date is the single most important determinant of who gets a patent.
With a provisional application on file, you can feel safe promoting your invention. Finally, if you significantly improve or change your invention after filing your provisional application, or decide not to go forward with a non-provisional application, the lower cost and turnaround time of a provisional application means that you haven't gone through the more costly and difficult non-provisional process prematurely or unnecessarily. Finally, multiple provisional applications can be combined into a single, later-filed non-provisional application--if your first provisional application sufficiently details the invention that appears in your non-provisional application, you can get your earliest possible filing date for the entire invention!