If you want to enable automatic login on Mac OS X remotely you can to this by using ssh and the niutil command. This requires that you have enabled "Allow remote login" in the System Preferences, of course.
1) Open an ssh session to your Mac.
2) type su to become root.
3) To enable the automatic login, the property "username" must be found by loginwindow in the local netinfo database. Here is how you do it:
niutil -createprop -t localhost/local /localconfig/autologin[space](NOTE: shown on two lines; replace [space] with an actual space character and enter on one line)
username user_to_log_in
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010510052218857