Richard,
A couple of notes:
1. Typically, the taxiway network will have a parallel taxiway to the runway. These are usually identified by letters, A, B, C, etc.
2. Then you will have taxiways that run from the parallel taxiway to aprons, entering and exiting runways, etc. These can be by the letter of the parallel taxiway with a number following, so that a series of entry/exit paths to the runway from taxiway A would be A1, A2, etc.
3. A simple plan is to simpy work from north to south or west to east...just start at one side and work your way across, first parallel to the west becomes A, next one becomes B, etc.
4. Then you go back and hit the smaller paths that connect them with A1, B1, etc.
5. There is not a set rule on this. Sometimes you just make a judgement call.
The designators are used by ATC in the game to give you directions when asking for taxi clearance.
Derrick