Your child must apply in person with both of his parents or guardian. If only one parent can appear, you will need a notarized statement of consent from the other parent, according to us-passport-service-guide.com.
You will need to fill out an application for your child's U.S. Passport. The form must be signed in front of an authorized agent, according to travel.state.gov.
You will need an original copy of the child's birth certificate, a photo ID of the child and two passport sized photos, according to us-passport-service-guide.com. The person applying for the passport on the child's behalf must establish his relationship to the child, if it is not certified by the child's birth certificate.