To get more infos about this tweak, look at the links above.
You have to do the following steps: (note: you have to change the partition to your needs. In my case its: "/dev/sda8 /")
1) edit your /etc/fstab and add thing marked bold to your mount line.
/dev/sda8 / ext3 defaults,noatime,nodiratime,errors=remount-ro,data=writeback 0 1
2) edit /boot/brub/menu.lst and add the bold marked entry.
kernel /boot/vmlinuz26 root=/dev/sda8 ro vga=865 rootflags=data=writeback
3) it can be necessary to run update-grub after that. But its not necessary on my archlinux system.
4) To prefent errors add the new mode to your filesystem before reboot.
tune2fs -o journal_data_writeback /dev/sda8
5) to see if the changes went right, check it with:
tune2fs -l /dev/sda8
(you should do this again after reboot)
have fun with a faster performing system. ;)