Show up earlier for biometric appointment at ASC?

The way USCIS works is that a lot of the people are instructed to show up at the same hour (more or less like the airlines overbooking their flights in the hope that some people will cancel or fail to show up) and that means that when you have an appointment at 1030AM, no one is waiting specifically to deal with you.  The agency just gets a bunch of people and then processes them as fast as they can.  Generally this means that you have to just wait, sometimes very briefly and at other times a lot longer depending on how you end up in their line.  This, however, does not mean that you can arrive late, because they might throw you out of the system and categorize your application as abandoned.

Now, a lot of people would rather go early for an appointment.  This is possible in some locations but not a guarantee.  On occasions, even the security at the entrance to the building may not allow you to enter (the building may have a limit on how many people can be in at the same time).  On other occasions, you maybe able to complete your fingerprinting even before your appointment time, and there are reports that you can do that even days ahead.  This should only be tried if it would not make a difference that you are not allowed entry or you cannot get your fingerprinting done.  If a date and time is really inconvenient, it is best to call the USCIS and ask them to reschedule it for you.