A biografie can be explained as an account written about one specific person- about a chain of events that make up a person's life.

A Biografie writing firstly needs a good amount of research to be done on that person, his life, his attitudes, his principles and how he lived up to each one of them. You could make the biography stronger by using some quotable quotes from scientists, historians or even a artists. Thus you could make a beginning this way.

When you research on the life on who you are writing the biography, you have to collect even the minute details, so that the biography is made different, and interesting. You need to collect his life's experiences, and make them into attractive stories, as dull and boring facts do not make a good biography.
A biography should be a story which is not retold, but a story which would make the readers ask for more details, and make them more curious.