Once you get back to the generation born about 1900, you can find many records online and at courthouses, libraries, and archives. But you’ll need to start with more recent information on your parents and grandparents. You may already have dates and places of birth, marriage, and death, and you may already have stories about your ancestors.
Many times, cousins, even those younger than you, will have heard stories about your ancestors. Cousins, friends, and neighbors of your ancestors may have photographs of your ancestors, and newspaper clippings.