Kort : The law light style  is to make a photo without flash and only with the natural low light in the espace or room with a soft light... The best condition for to take this style of picture is the night. : http://www.blackphoto.com/tutorials/lesson_night.asp or
http://digital-photography-school.com/blog/how-to-get-better-digital-photos-in-low-light-conditions-without-using-a-flash/
(my 2 favorits webpages for the tutorials)