The quickest way to disable autostart of services in Debian is to utilize a convenient curses interface to selectively choose which services to autostart in different run levels. Its so much easier to use than update-rc.d.  Its good for instances where you are migrating services out of an existing box, such as removing the mysql server without uninstalling.

The package is called:
sysv-rc-conf

(Install it using aptitude or apt-get install)