If you are normally on a plain phone line like me, take your machine to work or another place with a fast connection to do the installation. Then try to make sure that you at least download all packages that you may want.
From the System menu, run the Synaptic package manager. Go into Settings/ Preferences/ and enable "Apply changes in a terminal window". (This is critical, because sometimes packages will ask you a question or give information. Ignore whining about not having a terminal.) Also enable "Show package properties in the main window."
In Settings/ Repositories/ enable the third party software repository. You probably do not need the sources. In Ubuntu, pretty much everything on the installation CD seems to get installed. In Debian, make sure that your installation DVD is included in the repositories. If it is in there twice, temporarily exit synaptic and fix it in /etc/apt/sources.list.
To select packages look for the main package name. Usually, you want the one without the version number, if there is a choice. Let Synaptic figure out the details of what exactly is needed to install a working version. In particular, normally you do not want the source, debug, or development parts of it. Something ending in -src, -dbg or -dev is likely of no use to you at all.
Select the package to see a description. Click the button next to the package and select "Mark for installation." Then click apply on the tool bar. If you just want to download the package and have not yet decided to install it, click that button.
Next is a list of packages that I installed, to give you an idea. Many will be of no use to you, some might. OK means that I found it already installed. Remember that this applies to downloads May 2009. Things may be different when you read this.
If you are on a phone line, you probably want to save all these downloaded packages to a DVD. In that case, if something bad happens, you can get them from the DVD, instead of again downloading them from the Internet.
To do so, you need to have package aptoncd installed. From the System/ Administration/ menu run aptoncd and select Create. This then creates an aptoncd....iso file that must be burned to disk.
Unfortunately, Ubuntu comes at the time of this writing (5/09) with a gnome CD/DVD writer called Brasero that is unable to do so. Therefor, use the good old dvd+rw tools that do work, (and for that reason were replaced by Brasero that does not.) In a terminal, cd to the location of the aptoncd...iso file and enter
growisofs -dvd-compat -Z /dev/dvd=aptoncd....isoYou can delete the aptoncd...iso file again to save disk space.