This might be more useful here.
The Rules to the power of Geass, as observed in the episodes thus far.
The user can only use it once on a same individual. Any following attempts will be ineffective.
The victim is bound by his or her physical and mental capabilities. Asking the victim about or to do something that he or she doesn't know or cannot do will produce no effect.
The user must have direct eye contact with the victim. The power cannot work over telecommunications or monitors, or even a layer of semi-transparent substance.
Direct eye contact via a reflective surface, i.e. mirror, will be enough for the power to work.
The power will work within a 270-meter radius of the user.
The user may give as many commands as he or she wishes while direct eye contact is maintained.
The user must give the commands verbally. However, the power of Geass will control the victim for the duration of what the user's command indicates, so the victim may still act under the power's influence even when direct eye contact is broken.
The user may use the power on as many people as he or she wishes simultaneously, provided that they meet the above rules first.
The victim will not retain any memories from the time during which he or she is under the influence of the power of Geass, due the rewiring and damage of the brain. For same reason, the victim gains immunity against following attempts of the power being used on him or her.