We all went through the process of searching, applying, waiting for results, being rejected, and fortunately being admitted to U.S. universities.. So, we know what a hard time this is!
You can find tons of information regarding paperwork, visas, courses etc at Stanford’s website. You may also find useful tips and details at this site (credits to Manos Pontikakis). Though, if you want something more informal, send an email to one of the members of the board, and we will try to bring you in contact with somebody close to your related study field.