To obtain a US passport for your first time, you must apply in person. Application locations vary depending on your location.....but your local USPS post office usually offers them.
Passports require a passport picture, original birth certificate, and picture id. Travelers under eighteen will need to go with a parent, and the parent must also bring all of their forms of identification.
The passport picture must be 2 inches by 2 inches. Usually the post office will offer you to buy these pictures from them for around $15.00. Other options include going to the local photo center or K-Mart which will do them for about $7.00. Another option is to make your own digital picture with the guide the Department of state offers*.
The cost of the passport at application center is $97.00, and it should be processed within about 6 weeks. If you are a student, the process generally goes faster than adult visas, due to the shorter background check performed on the applicant.
For more information, visit the State Department's official site for passports. Enjoy.