There are no 'Idiot's guides' to this subject, there are customer Admin courses at Beeston Nottingham but no books nowadays as things are always on CD's.
Brief out line is COS 'Class of Service' :-
LCSD List class of sevice definitions.
What do you want to allow the telephone to do,
Do you want to allow it to divert calls?
So AED and ADP must be in its COS.
Make an O/G call with someone on hold OGH must be in the COS.
You can then build a COS's 0-31 with all situations covered.
Normally COS 0 has only PAX in it which will only give dial tone and the capability to dial another extn within its own pabx, COS 31 can do every thing from Trunk select to Executive override (cut into calls).
Brief out line TAC Trunk Access COS. :-
TAC is again Classes 0-31 and is listed by the command LTGA List Trunk Group Access.
This provides a matrix between the TAC and the Trunk Main Group so you can decide who is allowed to dial where, this also starts to bring in time zones, (Its now getting too deep!)
On the back of the TAC's you also have Route Restrict Tables listed by LACR (TAC)in these tables there are BAR & Allow Tables, this gives even greater control over who can dial what.
For example x24345 COS 12 Tac 3, TAC 3 allows all inter pabx and all inter network calls, but against his public outgoing Tk Gp is RRT 1 with an international office number
900312345678987 and this is allowed,
The story behind this waphel is he cannot dial his Mother around the corner but can dial the office in South Africa.
Next will be Least Cost Routing and more Bar & Allow tables,
Time of day Barring ARRRRRH......
Without proper courses and a lot of trial and error Good Luck.....
Mal.