Schedule your appointment at the U.S. Embassy or Consulate as soon as you receive notice that you have been granted an I-20.
Many embassies/consulates recommend that appointments be made no more than 90 days from the intended date of travel, but some can make earlier arrangements for interviews.
Note: In most cases applications must be made in person. Remember, the Officer has the final word on your application; his or her judgment is not subject to review. Standards for visa eligibility may be considerably more rigorous than the standards you must meet to qualify for a Form I-20. Use good judgment as to whether to submit additional information with your entry visa application.