Q: How to change the timeout seconds for GRUB menu on boot-up?

1. Read General Notes

2. sudo cp /boot/grub/menu.lst /boot/grub/menu.lst_backup
   sudo gedit /boot/grub/menu.lst

3. Find this line

   ...
   timeout         3
   ...

4. Replace with the following line

   timeout         X_seconds

5. Save the edited file (sample)