Most of the questions asked by DebianInstaller can be preseeded by setting the answers in the debconf database. This can be used to do automatic installs. The installation manual explains how to set up preseeding: http://d-i.alioth.debian.org/manual/en.i386/ch04s07.html#automatic-install and includes a complete example. Feel free to add any information that is not covered in the manual to the notes below.
Post here any links you have to example preseed files. Note that using any of these files directly is not wise, as a malicious person could probably come up with values for a preseed file that makes d-i misbehave. Also, the files are downloaded over http, so are vulnerable to man in the middle spoof attacks. The best way to use any preseed file is to copy it to your own local web server or media, and look it over before using it.
Joey Hess's modular/hierarchical preseed configuration, supporting installs via usb keychain or netboot with varying configurations for different machine types. http://kitenet.net/~joey/d-i/preseed
Christian Perrier's page documenting automated d-i installs in vmware, using netboot. http://people.debian.org/~bubulle/d-i/vmware-fai.html
Simon Kirkby's fully automatic basic install. !Warning! will format machine without asking. http://interthingy.com/digby
Holger Levsen's d-i examples showing a way to preserve partitions and ssh-host-keys: http://layer-acht.org/d-i/
Phil Hands' d-i setup, that allows minimal (i.e. no exim) installs, works from CD, PXE & USB (read the HOWTO's), and allows custom configs to be specified at the boot: prompt http://hands.com/d-i/
DebianInstallerAsSshClient for using d-i as a ssh terminal
- Do not work off a debconf-get-selections (--installer) generated preseed.cfg but get the values from it and modify the exmple preseed file with them.
- Be aware there is only one space in preseed files between subkey and value on "owner key/subkey value" lines.
- Do not reboot in the base-config/late_command command, the installation process will start again at the start of the 2nd stage.