System/preferences/sessions:
now I'm not sure if you really want beryl manager or compiz fusion.
Beryl:In startup programs tab click on button NEW. Under the
name type anything you want like "beryl"etc.. under
command type
beryl-manager.
Click ok and it should start beryl manager automatically when you start Ubuntu.
Compiz fusion:For compiz, i have an application called compiz fusion icon, which looks similar to beryl manager and it sits in tray.
if you want it:
http://ubuntuforums.org/showpost.php?p=3163821&postcount=8
Under System/preferences/sessions: Click NEW, under
name type whatever and under
command type
fusion-icon------------------------------------------------------------------------------
If you dont want fusion icon, then ..System/preferences/sessions:
Click NEW, under
name type whatever and under
command type
compizAs for default opening applications, Right click on file -> Properties -> Open With -> Select the correct program or click 'add' to add an installed program to the list of options.
I dont have much experience with kde and xfce, so i cannot help you with. Cheers!