Many of the USCIS applications for immigrant status in the U.S. require a Federal Bureau of Investigation (FBI) criminal background check before approval. This process is conducted by appearing for an "ink" or electronic fingerprinting for government processing at a designated time and place as listed in a notice that will be provided by the USCIS. This FBI criminal background check is normally completed with about 30 days after your appointment and it is a good indicator that a USCIS interview may be following shortly thereafter. So don't make extended trips until you get the interview date. Generally, a fee was previously paid to complete this biometric appointment at the time the initial application was filed. Consequently, there is no additional fee due at the appointment.
The notice will reference the type of application for which these biometrics are to be taken so bring it to the appointment. Also bring a valid and current passport, driver's license, birth certificate, perhaps a marriage certificate and all other documents required on the notice. Also, drug testing is not part of these biometrics although it may be part of a necessary medical examination conducted at a different time.
At the fingerprinting, do not bring a cell telephone, digital camera nor any food or drink. A body scanner for weapons is employed at entry. Also, try and leave small children and babies at home or with someone in your car if at all possible. These appointments are usually over in a fairly quick fashion. Attorney presence is not needed. Upon completion of the process, the FBI results are good for 15 months. Finally, if you are unable to attend your appointment the notice form outlines procedures for rescheduling.