How to clone packages setup

["Robin Rowe" <rower@movieeditor.com>]

Hi. How do I clone my packages setup?

I want to install the same packages that I have installed on one machine to
another machine that just has a basic install. What configuration files do I
copy and what command do I issue to cause apt-get (or whatever) to fetch and
install the same packages on the second machine?

There are two different ways I may need to do packages setup cloning. Either
the packages would be exactly in sync, or I might need to add packages but
not uninstall any applications that a user may have added on their own. How
do I do that?

Any pitfalls if one machine is Potato and the other Woody?

Is there a how-to for this somewhere?

Thanks!

Robin