Hello Astro Guy,
Nice looking setup. I've been getting up and running with a CNC Taig also, but I've spent some time on a manual mill which has helped me.
I'd say "home" would be a location where the spindle axis is near the left front corner of the table (assuming you are facing the table), with the Z axis several inches (For a Taig, 6 to 7) above the table. However unless you have homing or limit switches installed, you cannot really home the machine anyway. You could set "machine zero" at these locations though.
The other, and very important, zero point is the workpiece zero and this depends on the part you are making. If your part blank is rectangular, you might set workpiece zero at the left front corner of the workpiece. Workpiece zero in the Z direction will probably be the top surface of your workpiece. If the part was circular, X and Y zero would probably be on the centerline.
Have you read Section 7, Coordinate Systems, Tool Tables, and Fixtures in the "Using Mach3 Mill" manual? There is also some information on touching off to determine your workpiece zeros in Section 7.
Another good resource is the Yahoo Taig group and also Peter Smid's CNC Programming Handbook has some good information.
I hope this helps a little. Keep reading and asking questions.
What sort of parts or objects will you be making on the Taig?
Good luck.
Regards,
Chuck