Some part of the /etc/ssh/sshd_config:

ListenAddress <your public IP address>

AllowUsers <your user name>

ServerKeyBits 1024

LogLevel VERBOSE

LoginGraceTime 20

PermitRootLogin no

X11Forwarding no

/etc/hosts.allow

sshd : <IP> : allow

http://www.openssh.com/
https://help.ubuntu.com/community/AdvancedOpenSSH