The majority of people assume an autograph is the same as a signature. There are some very important differences.
A legal signature can be anything at all and does not have to be legible. As long as you sign all your legal documents in the same general manner, it is binding in a court of law.
An autograph on the other hand, must be legible enough to satisfy your fans and it should not be confused with your signature.
As a case in point, a fan may hand you a pretty document and in your rush to get to an appointment, you might just scribble your name. If you autograph it as if it were a book jacket, that shows you were there in your celebrity persona. If that document happens to be an agent agreement or power-of-attorney contract, it can easily be argued that you did not legally sign it.
On the other hand, if you use the same signature for both legal documents and fan collectibles, you may one day find yourself in a tight spot.
Consider as well, that an autograph should be fairly quick and easy to create. That is why an aspiring author should practice it regularly. After all, once you’re famous, you’ll find yourself facing a horde of adoring fans at the next convention and won’t have time to think about it.
Good luck and be sure to pace yourself to avoid writer’s cramp.