Provisional Patent

Straight from the USPTO website. http://www.uspto.gov/patents/index.jsp

"Provisional Application for Patent Filing Date Requirements
The provisional application must be made in the name(s) of all of the inventor(s). It can be filed up to 12 months following the date of first sale, offer for sale, public use, or publication of the invention. (These pre-filing disclosures, although protected in the United States, may preclude patenting in foreign countries.)
A filing date will be accorded to a provisional application only when it contains:
a written description of the invention, complying with all requirements of 35 U.S.C. §112 1 st paragraph and any drawings necessary to understand the invention, complying with 35 U.S.C. §113 . If either of these items are missing or incomplete, no filing date will be accorded to the provisional application.
To be complete, a provisional application must also include the filing fee and a cover sheet identifying:
the application as a provisional application for patent;
the name(s) of all inventors;
inventor residence(s);
title of the invention;
name and registration number of attorney or agent and docket number (if applicable);
correspondence address; and
any US Government agency that has a property interest in the application.
Form PTO/SB/16, available on the printable forms page of the USPTO website at http://www.uspto.gov/forms/sb0016_fill.pdf be used as the cover sheet for a provisional application."