The best way to secure your network with it is to simply plug it in between the Internet and your network. By default all outbound traffic (to the Internet) will be allowed (assuming you set up NAT rules as necessary) and all inbound traffic (from the Internet) will be denied.
If you don't specifically allow any inbound traffic into your network then "ip audit" is not going to be of much use to you, and "ip verify reverse-path" will benefit the rest of the Internet community by not allowing any of your internal PC's to send out spoofed packets.
If you need to allow inbound traffic make sure to only allow the bare minimum in, that is specifically define the protocol, port and destination IP addresses in your access-list. Turn on protocol inspection using the "inspect ..." command if there is an inspection for the protocol in question.
Set up a syslog server and log all your level 1-4 syslog messages to it and archive them off for future reference.
Other than that, have fun and relax.
