Hi,
Some ceran cook top cleaning and conditioning tips...
http://www.applianceaid.com/cerantop.html
If the pot doesn't touch the ceran glass full the heat will not be transfered from the element to the pot.
Ceran ( glass ) flat cook tops. Ceran cook tops can be easier to keep clean as there is no bowls or rings to worry about, but your cookware must have a very flat bottom.
Whirlpools FAQ might help as well,
linked here.
jeff.