Since the USPTO has instituted the "First to File" posture, Focus On Patents, Inc., is now recommending that inventors file a provisional application as soon as possible after completing an enabling description. An enabling description implies that a person familiar with the field of the invention would be able to make and use the product/process described in the provisional application.
Print your name and the date you first conceived of the idea on at least one sheet (preferably all) and sign your name next your printed name. For the date of conception, use the earliest dated document which includes some element of your invention. Preferably, you have kept a written record of each step of your inventive process in a notebook which could be witnessed along with your written narrative. If not, an invoice or order form for parts or notes in your day planner could be suitable. Remember to sign and date each sketch or drawing as well.
Have it witnessed:
Leave space on each sheet to have two trusted persons, not related to you, witness your invention. Each witness should understand your invention from the written record and should sign over his/her printed name and put the date of review next to the signature. The witnesses should be persons who can and will attest to your invention in case you are no longer able to do so. You might ask your clergy person, attorney, insurance agent, teacher or consult the services of a registered professional engineer, architect, land surveyor or a registered patent practitioner.
Determine Filing Status:
Small Entities are individuals or small companies having fewer than 500 employees. Micro Entities are small entities that also have 1.) no more than four other U. S. Applications, 2.) ave a gross income the previous year that is less than three times the median household income for the preceding year and 3.) have not assigned the application to an entity that would not qualify. All inventors named on the application must qualify for Micro Entity status. See http://www.uspto.bov/patents/law/micro_entity.jsp for the current income limit.