Do not upgrade your system to 13.04, which is very slow.

1. Install gnome-shell
Press CTRL+ALT+T simultaneously to enter terminal.

sudo apt-get install gnome-shell

log out and choose "gnome classical no effects" to log in

Note: To add and remove application launchers in the gnome-panel you need to:

Press Win+Alt and right-click the top menu bar - N.B. Win is the Windows Symbol key
2. uninstall unity and compiz
   sudo apt-get remove unity
   sudo apt-get remove compiz
3. to replace Ubuntu Software Center with Synptic
uninstall ubuntu software cente

   sudo apt-get remove software-center
   sudo apt-get autoremove software-center

install synaptic

   sudo apt-get install synaptic

Install Gdebi Package Installer for installing deb package manually.
sudo apt-get install gdebi

4. Remove Ubuntu One
  ‘Ubuntu One’:

   sudo apt-get autoremove ubuntuone-client python-ubuntuone-control-panel

5. remove indicator-messages

‘indicator-messages’ :- It’s a small icon on the top bar on your desktop that allows you to access various social apps and their settings (such as Gwibber, Empathy etc).

sudo apt-get autoremove indicator-messages
sudo apt-get autoremove telepathy-indicator

6 remove Deja-dup
‘Deja-dup’: If you don’t use this file backup tool, use the below command to get rid of it.

sudo apt-get autoremove deja-dup

7. Remove Zeitgeist
‘Zeitgeist’: As said above, this is a major component in Ubuntu. If you don’t need it, and because it too has few services that occupy my RAM, use the below command to remove it.

sudo apt-get autoremove zeitgeist-core

8: Replace Totem with Smplayer

sudo apt-get remove totem
sudo apt-get remove rhythmbox
sudo apt-get autoremove
sudo apt-get install smplayer

9. install gconf-cleaner
sudo apt-get install gconf-cleaner

Run gconf-cleaner
gconf-cleaner

10. Clean cashes and un-used dependencies
sudo apt-get autoremove
sudo apt-get autoclean

Other Option: Install bum to remove ‘unnecessary’ system services, manually

sudo apt-get install bum

Then use the below command to launch it.
gksudo bum