How to have a clean *ubuntu and Awesome WM?

I would advise you to go with Xubuntu (last LTS or latest).

1. Install Xubuntu

2. Install awesome

   sudo apt-get install awesome awesome-extra
   

   If you want the most updated version, run before:

   sudo add-apt-repository ppa:klaus-vormweg/awesome
   sudo apt-get update
   

3. Remove Xubuntu desktop.

   If you don't remove these package, it will override the awesome background and can conflict with apps if you don't set specific awesome rules.

   sudo apt-get remove  xubuntu-desktop xfdesktop4
   

4. Set awesome as the default WM

   sudo xfconf-query -c xfce4-session -p /sessions/Failsafe/Client0_Command -t string -s "awesome" -a
   

5. Set awesome to autostart

   ln -s /usr/share/applications/awesome.desktop ~/.config/autostart/awesome.desktop
   

6. Restart lightdm service

   sudo service lightdm restart
   

With this configuration, you have a lightweight, updated and fast Ubuntu Awesome. To help you customize Awesome, I would advise you to look at the awesome-copycats.