A small tip that will make you save much time for starting or stopping your Ubuntu session: Instead of choosing "Stop", choose "hibernate".
Note that: The machine is physically turned off (drives will be stopped). But when you turn on, you should resume your previous session (applications and windows).
You do not need to save your documents and close them before stopping the machine.
No need to close your system to restart.
You find your applications and windows in the exact state where you have left them.Your system will start faster.
The "hibernation mode" is very different from sleep mode. In standby mode, the computer is not really turned off, as the CPU and memory continue to consume electricity. The "hibernation mode" Ubuntu really turn off the computer.
The hibernation option of Ubuntu is available on all machines, even on laptops and desktop.
Network connections will be cut off. If you were being downloaded by Peer-to-peer (BitTorrent and others), the download will resume automatically once you start up your session.
In the case that you have a dual-boot with Windows. If you have something to do on Windows, choose "hibernate", restart on Windows and then switch back to Linux:
Take the habit of saving your files before you hibernate, you never know what could happen.
Data from ongoing programs are stored on the swap partition. Therefore better allocate enough space for your swap file (at least 1 GB).