1. First and foremost, you need to backup all your important files.
2. Next, make sure the repository is updated: sudo apt-get update
3. Open the Update Manager with this command: sudo update-manager -d
If there are any updates to install, use the Install Updates button to install them, and press Check again after that is complete.
A message will appear informing you of the availability of the new release.
The Update Manager will open and you will now see the upgrade option. If you are brave enough just go on. Follow the on-screen instructions.
4. Now sit back, relax and hope for the best.
If the upgrade process is successful and everything is working well, congratulations and have fun with Ubuntu 9.10 Karmic Koala.