If you’re working with a good adoption agency, they’ll have up-to-the-minute information on what each country wants to see from your dossier.  But in case you ever want to double-check what you’re hearing, check with the U.S. Department of State. 

The requirements your agency gives you should at least cover everything listed here. 

Also useful for checking the status of currently-”closed” countries (we keep an eye on Guatemala, ourselves, since our twins were born there).