You can change your party affiliation by obtaining a Voter Registration Form from your state's Board of Elections, indicating the change and sending the form back. Each state has its own unique requirements and deadlines regarding registering or changing party affiliation.
In those states that list party affiliation on voter registration, you can just fill out a new registration form and check the box for a different party. Irrespective of your party affiliation, you can vote for any party's candidate in the general election.
Patrick Seyd has written: 'Labour's grass roots' -- subject(s): Labour Party (Great Britain), Party affiliation 'Labour and Conservative Party members 1990-92' -- subject(s): Conservative Party (Great Britain), Labour Party (Great Britain), Party affiliation, Political activists
Party affiliation is not required at registration. However, on Election Day, Georgia voters must declare an oath of intent to affiliate with the particular party for whom they are voting on Election Day.