Before you do this make sure you have created another user in the wheel group.
To disable root login through ssh, edit the following file:
# /etc/ssh/sshd_config
browse to the following line:
PermitRootLogin yes
and change to:
PermitRootLogin no
Save the file and restart ssh.
# /etc/init.d/ssh restart
If you are ssh’d into the server with root when this is done, your connection will fail on the restart of ssh.