The I-94 form is a declaration of what goods you are carrying into the country from foods to cash. Fill it out completely and correctly, then when you pass through immigration at the U.S. port of entry the inspector will make a notation of the date of entry and mark your visa status, then staple the I-94 onto your passport.
Animals are usually sent to Coventry by the American authorities despite what steps you take beforehand. Make sure to have the animal up-to-date on all medical treatment including shots and have had it examined by a veterinarian within the last 30 days.
For a complete list of custom requirements and to search for particular information, go to United States Customs.