With Passports now required for travel to even Mexico and Canada* getting a passport before you need it is wise. If you have never had a Passport or yours is older than 15 years or you were 16 before receiving it follow these instructions.
You will need:
To apply in person
Form DS-11 completed
Proof of citizenship
Proof of identification
Money to pay for the processing
*If you are traveling by land or sea to Mexico, Canada, the Caribbean, or Bermuda you can use the Passport Card
which applications are being accepted for beginning on February 1, 2008.