There is a step by step guide for this, in steps 3,4, and 5 of:
The Very Verbose Debian Installation Walkthrough
http://osnews.com/story.php?news_id=2016
It basically teaches you how to partition with cfdisk, creating /boot, /root, and swap, i usually do not create a /boot one. If you want /home, /var, /tmp, etc, just choose Logical instead of Primary for those ones, the max number for Primary partitions is 4.
HTH,