Going from Fedora to Ubuntu

Instead of executing su, we have to execute sudo; this command will ask you a password. Just introduce the user password. If you want to be root you have to make
$ sudo su

Basically instead of yum we have another command, namely apt-get. Its use is as follows (more details executing $ man apt-get):
sudo apt-get install nameprogram
sudo apt-get remove nameprogram
sudo apt-get search nameprogram
sudo apt-get update nameprogram

examples:
$ sudo apt-get install thunderbird

$ sudo apt-get install ubuntu-desktop #do this if you are using kubuntu, to install gnome

$ sudo apt-get dist-upgrade #this command updates all the packages of the system

apt-get requires a list of the sources. You can edit it:
$ kdesu kedit /etc/apt/sources.list



Some other packages that are worth to install are:
adept, kpackage #those are similar to yumex
to execute:
$ kdesu adept

amarok
kdm libdvdread3 #I don't remember what is "kdm"
libxine-extracodecs

koffice

Some pages that contain useful information:
https://help.ubuntu.com/6.10/book/book/ubuntubook-ch3-html/UsingUbuntuontheDesktop.html
https://help.ubuntu.com/6.10/book/book/ubuntubook-ch6-html/SupportandTypicalProblems.html
https://help.ubuntu.com/6.10/book/book/ubuntubook-ch7-kubuntu/Official-Ubuntu-Book-Kubuntu-Chapter.html

Finally, a good forum is www.kubuntuforums.net