Remastersys is must have tool for any Linux Ubuntu. I never forget to install this handy tool. Remastersys can be used for regular backup of your Ubuntu before crash may occur. After you have fresh install first you should install must have applications for Ubuntu 12.04. Then after you can go for Remastersys. To install Remastersys follow below steps.
1. sudo vi /etc/apt/sources.list
Paste below two lines.
deb http://www.remastersys.com/repository lucid/
2.Update recently added source list by executing
sudo apt-get update
sudo apt-get install remastersys
You have successfully installed remastersys on your machine.
[Though the source list is of lucid it works for precise also. ]