ok, weel, im the type that has to have every thing mapped out..
*introduction- of course, every introduction, needs an introduction :)
Many nonfiction books begin with an introduction where the author writes about her motivation for addressing the topic of the book. Introductions can be humorous, intellectual, brief or thought-provoking. Whatever type of introduction you want to write, make sure you give it the same amount of attention as you did any other chapter. Biographies are one type of book that benefit greatly from a well-written introduction. Learning how to write an introduction to a biography is easy, although making it effective takes practice and perhaps many revisions.
Read the introductions of several of your favorite biographies, making notes about what subjects the author covers. What style of introduction do you relate to? What information do you feel is important to address? Every author will answer these questions differently. Thats why I can give you a direct answer, sorry.
Brainstorm all the topics that you want to include when you write the introduction. Think about why you are writing this particular biography and what impact the subject has had on your life or the lives of others.
For example (I love people to give me examples, so if you don't like it thats fine, just extra help, it might be crap, haven't done biographies in class yet, just guessing)
say i was writing about Ian Somerhalder, first thing was go on google and find him on wikipedia, I love this sight!
Somerhalder was born and raised in Covington, Louisiana, raised a Cathlic, he attended St. Paul's, a private Catholic school in Covington, he as a young boy aspired to make a change in the world, anouther passion from becoming an actor. He beacame a model at the age of 10, then from the young age of 17, landing his first credited role in the film "Life as a house', then went on to become the famous man that he is known for today, a co-actor on the popular T.V series Vampire diaries.
then id talk about his major roles, his family, his values, the 'The Ian Somerhalder Foundation (launched on December 8, 2010, Somerhalder's 32nd birthday)'
good luck, btw, I got most of bits and peices of info from wiki, great site!