What You'll Need: DS-11 form (more info below), Proof of U.S. citizenship and a photocopy of this document(again read below), the fee (usually less than $200, pay with credit/debit card), and finally a passport photo (read more below).
Step 1: Get a copy of the DS-11 form. This is the official U.S. passport application. It can be filed online here, or printed off (pdf) and hand-written from here.
Step 2: Proof of citizenship can come from several different documents. If you were born in the U.S. chances are good that you have a birth-certificate, this is the first and most common document. If you don't have a birth-certificate, you can submit a Consular Report of Birth Abroad, a Naturalization Certificate, or a Certificate of Citizenship.
*make sure that you bring BOTH the actual copy AND a photo copy of this document!
Step 3: Make sure that you have approximately $200-$300 on a credit/debit card. I'm not 100% sure what forms of payment are accepted across the U.S. But I'm pretty sure that cards are usually the best option!
Step 4: Make sure that you have 2 appropriate passport quality photos. These can be taken at local pharmacies like Walgreens, CVS, and Rite Aid.
**BONUS: Google passport photo coupons and you might save like $10!!
Finally: Find-out where to apply! If you're in the U.S. click here. If you're outside the U.S. read more here.
Except to wait 4-6 weeks, and look for your citizenship documents earlier in a separate mailing! Once you get your passport here is why I think you shouldn't plan your trip too much!