You must send your physical passport- copies cannot be used for visa issuance.
Your signed passport must be valid and contain sufficient blank visa pages- visas are stamps affixed to the blank "visa" pages of your passport. Amendment pages (clearly marked as such) in the back of your passport are not acceptable for visa issuance.
Your passport's expiration date must be greater than six months from the date you plan to depart the country you intend to visit. If your passport does not meet this requirement, you must renew your passport or obtain a new one prior to applying for your visa.
If you are not a citizen of the United States:
A copy of your valid green card (front and back), a copy of your U.S. visa and original I-94, student I-20, I-97, H1B document, J1 including DS-2019, etc. is required.
Please note: in some cases the original green card is required to be presented to the Embassy or Consulate.