Customising Debian install

[Andrew Wood <a.j.w@me.com>]

Whats the best way to go about making a custom installation of Debian 
which I can then install onto multiple machines without having to go 
through and manually add extra packages and remove certain default 
packges from each machine?

For certain things like removing OpenOffice and replacing it with 
LibreOffice this approach works but is time consuming.  For other 
packages it just results in disaster, for example  Ive tried removing 
the empathy package and have inadvertently removed the entire OS.

How come the packages have dependencies like this, surely removing an IM 
client shouldnt also trigger removal of everything else.

As an example, Id like to remove things like Iceweasal and Epiphany so 
that theyre not installed by default but include our own custom Firefox .deb

Likewise Id like to do away with Empathy and Tomboy.

Surely theres a way to automate this and then build my own iso images so 
i dont have to customise each PC after installation?

Thanks
Andrew