These can be obtained at your local Department of Motor Vehicles office. You will be required to show your birth certificate, social security card and proof of residence. They will then take your photo for your card.
If you are a member of or retired from the armed services or are a dependent of one, your military identification card is acceptable for domestic flights. These can be obtained at your identification card office on your military installation. Be sure to check that it has not expired before traveling.
A current U.S. or foreign passport is acceptable as long as it has not expired. To obtain a passport, you will need to fill out a passport application and submit it with your passport photos and identification information to the appropriate U.S. passport office or your home consulate or embassy. Passports can take up to 8 weeks to receive in the mail, so plan accordingly.
If you are flying with children, check with your airline to determine what identification is acceptable when you check in. If your child is flying alone, you will need to show your identification as well as the ID of the person who will be meeting your child at his destination. TSA does not require children under 18 to show identification at security checkpoints, although they will be screened.