Security

passwords: not easy to guess or crack; change periodically?
firewalls: host-based or network-based, packet-filtering by IP or port, stateful inspection, (caching) proxy server
antivirus
install and running minimum services
updates/patches
backups
log files review
security protocols: IPSec, PPTP, L2TP, SSL/TLS, SSH, WEP/WPA
user training/education, procedures, policies