Its the same as any other firewall........dont allow anything thru' it unless your OK with it.
Pretty well much a pointless question really as no 2 pc's run the same stuff (other than work based pc's).
There are no shortcuts to setting up firewalls...as everyones idea of what is safe or acceptable (wether in or out) is different.
For instance there is no way that I would allow NERO/WMP/SVCHOST/GAMES/etc (a top of my head list here) thru a firewall for no valid reason..but plenty of other people would...think about it.
YOU set up the firewall and YOU accept responsibility for your actions....PERIOD.