Well there is defenetly no substitute for seat time. Baring that pick up a few books. My biggest recomendation is "Total Control"
other good ones are "Sport riding techniques" and "Twist of the Wrist". All of these books will have exercises you can do to improve your cornering.
The basic advice I can give you for better cornering
Have a light grip on the bars, dont strangle them
Dont over ride your ability. (If you tighten up, you are going too fast)
Look into the corner.
If you start to get scared DO NOT LOOK OUTSIDE THE CORNER, look far away from you at the yellow center line
Try to hold a steady line, dont move back and forth
Be smooth about everything.
Get as much practice as you can