If you believe that your invention may be protectable, then you should prepare a written disclosure of your invention which includes what your invention is, how it works, how it is used and how it is an improvement over devices which are similar to your own. To establish inventorship, you should sign your disclosure and have it cosigned by one or two others who are not also co-inventors. Also, be certain to track the dates of development of your invention. A diary can be helpful for this task.