How to change boot order in GRUB2?

With Ubuntu 9.10 (Karmic Koala), GRUB2 is the default boot loader.
How to change boot order in GRUB2?

1.
$ cat /etc/grub/grub.cfg
see the order of the wanted kernel. Starts from 0.

2.
$ vi /etc/default/grub
change GRUB_DEFAULT=0 value to wanted kernel

3. run
$ update-grub
to update

4. reboot and check with
$ uname -r
to see if correct kernel selected.