In his farewell address, George Washington warned against two main things: political parties and relying too heavily on trade. To find this information, you can start by searching for "George Washington farewell address" on an internet search engine. Look for reliable sources such as educational websites, government archives, or books written by reputable historians. One such source could be the official website of the Library of Congress, which provides access to primary sources like Washington's farewell address. By reading the address itself or summaries and analyses of it, you will find that Washington expressed concerns about the negative effects of political parties on national unity and the dangers of becoming overly dependent on foreign trade.