Save ports

[Bray Mailloux]

I ran an nmap -sS localhost which output

port         state         service
13/tcp      open      daytime
22/tcp      open      ssh
25/tcp      open      smtp
37/tcp      open      time
53/tcp      open      domain
113/tcp    open      auth 
587/tcp    open      submission

This BSD box will be serving solely as a router so few of the above 
services are needed (submission, auth, domain, smtp). How do I begin 
closing down these services?