I did FP at Philadelphia in late April. You need to carry your FP appointment letter, passport (they asked for it even though the letter did not say we had to carry it), license. Make sure you carry whatever is mentioned in your appt. letter. They will give you a form to fill out, and then you wait for a while. A person will call you to do some basic checking of ID and so on. Then you wait again for them to call you for finger printing. They give you token numbers and will call you by your token no. The FP is computerized, and they make sure your FP is of good quality by taking FP multiple times till they are satisfied. They will return to you the form you filled earlier, with some annotation. That will be a kind of receipt.
There is a wash room in the hall, so you can wash your hands before you go to the FP machine. No food or drinks allowed. I don't know about cell phone, as I did not carry one. They seemed to accept people even few hours before the appt time. There is a paid parking lot directly opposite the FP center. I was done with FP in less than 1 hour. No hassles, no tricks, no surprises.
Good luck.
Sammy
