Follow my guide, this guide will not work for the newer cards.  It's at http://bit.ly/JXr52p.

Also, Public Enemy #1 are risers.  Double, Triple, Quadruple check your risers.

A few notes about initializing cards.  If you do it over and over again, you might want to try this if some cards aren't recognizing:

cd /etc/X11
sudo rm *xorg.*
sudo atitool --adapter=all --initial
sudo service lightdm restart

This will get you ready to run ./cgminer -n (you must set the variables that are listed in every guide as "EXPORT").

Public Enemy #1 are RISERS.  If you're shuffling and reshuffling and it still doesn't work, try 1 card at a time.  Weed out the bad risers.  Try a working card on a riser of a non working card.  Risers are bad.  They are absolutely terrible quality and are being mass produced.