Hi,
If this will be your Internet router you want to configure an ACL applied inbound to the outside interface permitting only the traffic that should be allowed.
As well, you can have an ACL applied inbound on the inside interface to permit outgoing traffic.
You can use CBAC to inspect the outgoing traffic and allow the returning traffic for the established sessions.
The ACL and the CBAC configuration depends on the devices and services that you will have/provide.
Federico.