With testing in Oracle VirtualBox first I must to make changes as it is described here:
In /etc/inittab change
id:3:initdefault: [...] x:5:respawn:/usr/bin/xdm -nodaemon
To:
id:5:initdefault: [...] x:5:once:/bin/su - -- PREFERRED_USER -l -c '/usr/bin/startx </dev/null 2>&1'
Then I have to switch run level through GRUB as it is described here:
In /boot/grub/menu.lst find the Arch section (the default is '# (0) Arch Linux'):
# (0) Arch Linux title Arch Linux root (hd0,0) kernel /vmlinuz-linux root=/dev/sda3 ro initrd /initramfs-linux.img
Change the kernel line to:
kernel /vmlinuz-linux root=/dev/sda3 ro 5
and then finally I should do as it is described here:
Edit /etc/inittab and find the line that looks like similar to this one (delete # sign)
x:5:respawn:/usr/sbin/gdm -nodaemon