The first thing is that people who are eligible for jury duty are called. Generally the group eligible for the duty is based on citizens and legal permanent residents of the country. People from other countries who may be living on any other kind of visa will not be eligible. The calling is done by the court mostly on random basis and one can get called at anytime for possible jury duty.
Everyone who has been invited has to be in court at a given time and date and not showing up can lead to legal issues for the person who was called.
Once the potential pool of jurors has been assembled in court, lawyers from both sides question these potential jurors. Both sides ask them questions about various issues and try to establish whether the juror will lean more towards their cause or will be more inclined towards the other side. This comes with great practice and time. The more attorneys are used to questioning the potential jury members, the better they get at this craft.
In case someone has a genuine reason to not be a part of the jury or does not meet the criteria of selection that is laid down by the law, he or she can be excused before being questioned.
As they talk to the potential juror, it is at the discretion of both parties to accept or reject anyone. They are not required to give any reason and simply can challenge anyone’s nomination. Generally this is done when the attorney feels that the given person may have a natural leaning towards the other side and may give his vote to the other party. Once twelve candidates have been selected, the process is over.