How to disk cleanup after apt-get upgrade/install/remove cycles?

[Ramasubramanian Ramesh <rramesh@ti.com>]

All,

 Often one is not sure of the choices and strength of packages/utilities and tend to install
multiple utilies for the same purpose. For example I have about 3 or 4 cd players and assortment of
mp3 palyers etc. Sooner or later you see that a lot of left over packages exists in your system that
you no longer use.

I am wondering if there is a fool-proof way of cleaning up that eliminates all unused packages.
Specifically, if I installed package A that brought in packages B C and D due dependencies. Is there
a way to find out that B C and D are no longer in the dependency list of any packages after removal
of say A. This will allow me to systematically remove all unwanted packages.

My naive approach now is

   1. do a get-selection to see installed packages
   2. mark the ones that you do not need
   3. try apt-get -s remove them to see if any thing else gets removed.
   4. Based on above output prune the list down so that step 3 produces 
      expected results.
   5. Go ahead with the actual removal

Are there any better methods? In particular is there a method to draw/list a directed graph of
dependencies of pacages in the current debian installation?
(or for that matter, do the dependencies form a digraph?)

Thanks for your help

Ramesh