Yes you would definitely need a visa to travel to the USA. Although you have not mentioned which country you belong to, as this would have helped me in giving you the exact information. However, the basic requirements are a valid passport, a visa, statement of proof of funds to support your visit and all the information on your friend that you wish to visit. Also, here is a link that will help you with all the details of how to travel to USA for tourism purpose:
www.airnz.co.nz
www.airnz.co.nz
