Session start up scripts

[AG <computing account googlemail com>]

Hello

Gnome 2.6 on up-to-date Debian Squeeze using 2.6.30 kernel on a single 
user system:

I have a couple of difficulties resolving what services, etc., are 
started at login.  I have used System -> Preferences -> Sessions to 
identify the services and applications I want started.  This includes 
using xscreensaver (rather than Gnome-screensaver) and Conky.

However, each login, so gnome-screensaver is initiated and Conky isn't.  
Whilst these aren't major issues, I wouldn't mind sorting them out, so I 
was curious if there are textual configuration files that I can hack to 
set this up.

Also, how does one override (default?) applications that are started 
when a removable media is loaded?  I don't want to use Totem (but don't 
want to uninstall it either) as my default media player for DVDs, but 
despite changing this in Preferred Applications option, Totem is always 
initiated when a DVD is inserted.  Again, are there some textual 
configuration files I can access to set my preferences directly to use 
VLC, for example?

Thanks for any assistance in these matters.

AG