Information taking from this website:
http://helpforlinux.blogspot.com/2009/04/6-ways-to-make-ubuntu-fast.html

And then goto /etc/event.d/ and change the ttyx files that you DONOT want. Edit them and comment lines starting with “start on runlevel”. So, in this case, you’ll comment the start line in tty4..tty6 files.

1. gksudo gedit /etc/event.d/tty4
2. Comment out where you see start on runlevel.
3. I usually do tty4, tty5 and tty6