What are the guidelines for a drawing to be included with a provisional application for patent?

Drawings (illustrations) submitted with a provisional application can be informal. That is to say, they do not need to be in any standardized form. However, the U.S. Patent Office strongly recommends submitting very specific drawings that adequately depict your invention. This is because highly detailed illustrations make it easier for the U.S. Patent Office to later associate the non-provisional patent application you file with this earlier filed PAP. LegalZoom can also help you obtain professional illustrations.

Please refer to the education center, "Drawing(s) of the Invention" under the "Filing Requirements for Provisional Applications for Patent" header.