FreeBSD Security:
Installation
Minimal FreeBSD 9.0 install

Configuration
Modify /etc/ssl/sshd_config
Modify /etc/ttys
Modify /etc/hosts.allow

Turn on pf, or stick it behind a firewall.

Security Checks

Run nmap against the server
Are you running DNS?  Check if Open Recursion (from external):
dig yahoo.com @ns1.yourdomain.com
Open Resolver Project
Are you running Mail? Check if Open Relay (from external):
telnet mx1.yourdomain.com 25
HELO client.domain.com
MAIL from: test@test.com
RCPT to: validemail@yahoo.com
(Should receive "Relay access denied" at this point)

Third-party test open relay