The main character is the cornerstone of the story’s foundation, be it fiction or historical. The main character will carry the story line, and all the other characters will play off of the main character.
In writing characters for works of fiction, contemplation and invention are the first steps for a writer. The key is to invent characters that the reader will identify with. The rule of thumb here is if you like your characters, so will the reader.
Multi-dimensional characters that become fictional real people are not so difficult to invent. The key to this is to take people that you may know and puzzle together fragments of traits and personalities to invent fictional characters. As in putting together a puzzle all the pieces must fit. If they do not then your character may be read as a little sycophantic, “apple polisher”. A little sycophantic however is a good trait for an antagonist, or “Bad Guy”.
A reader wants to be entertained and a good well developed main character goes a long way in getting the reader involved with the story. The core of any well remembered main character is honorable intentions. This holds true for even with the “Anti-Hero” types.
Life experiences is a basic foundation of knowledge for a writer, and a good imagination too, however barrowing directly from other writers, like script writers for TV and Movies is not using what you know or have done. A well thought out story from your own imagination will get you noticed. A good well thought out main character will make you a creative writer.