Merriam-Webster simply defines a signature as "the name of a person written with his or her own hand." A signature can even be as basic as an X. No special procedure exists to legally change a signature, however, when people do want to enact a change, they must do so on several documents so the new signature matches all their others.
A driver's license bears a signature, and if a person wants to sign his name differently, he must go to a local department of motor vehicles (DMV) and obtain a new license and sign with the new signature.
Another important identifying document, the passport, should be changed to reflect a new signature as well.
Bank Signature Card
When people open bank accounts, they sign a signature card. A person changing his signature should contact his bank for instructions on changing this card.
A person should request new credit cards, then sign the back with the new signature. This way, all signatures match.