How and how much do you monitor your children's media use?

Vicki Rideout, director of the Kaiser Family Foundation's Program for the Study of Media and Health (www.wff.org is the place to find all their reports), advises parents to 'stop and take a look at what's happening with your kids,' according to a Boston GLOBE article Thursday Feb.4.
 
Joan Anderson, author of the article, called the digital world 'a maze of menace and opportunity' and, quoting Rideout again, wrote that guiding parents through it is a 'job more parents should take to heart.'
 
I would like to know how parents are supposed to do this. How do you do it? Thankfully I am no longer responsible for guiding my sons who are grown and on their own. They are the ones who guide me, more often than not, with media use.
 
A resource mentioned in the article is a book Kids, Parents and Technolgy by Eitan Schwarz (Northwestern University): Dr. Schwarz urges parents to plan media as you would plan meals, since in either, kids 'will mostly consume junk.'  Easier said than done.