If you are utilizing 800 or freephone services, then you want to count those trunks individually, and keep them as thier own service of incoming only. The reason for this is you need to route the traffic to a long distance provider, which will be connected via their own trunk groups. If you do not seperate them then your PBX will be routing outbound calls to these trunks which would be a bad thing.
For local trunks, it is best to have them as bidirectional, or ISDN if possible. ISDN signaling will enable you to provide incoming exention information from the central office switch for Direct Inline Dialed extensions.
As for outbound long distance, you can include this in your bidirectional trunks as well, since dialing a “1” will route the call automatically to your long distance provider (if you are in North America). The only reason I can see to not include your outbound long distance in your local trunking is if you have dual long distance providers, say one for national and one for international.
Author: McGraw-Hill illustrated Telecom Dictionary.