CIDR and Classless subnetting

This will be a real quick question, and responses should be sent directly
to me, rather than the list please.

I am trying to find more information about variable length subnetting. I
have read the CIDR RFC, the VLS Table for IP v 4 RFC, and still am not sure
about how to make it work. I have been accustomed to only subnetting class
C networks. As I begin to implement the smurf amplifier blocking on our
border router, it has come to be that I need to obviously get a better
grasp. If any of you might suggest some recommended reading on this topic
so I can quickly freshen up, it would be greatly appreciated.

Thanks for answering the "junior" member of the list.

Kevin Brown
Huber & Associates, Inc.