Newbie: G Code Programming Question

I'm just starting to CNC program in G-codes. I'm uing MillMaster
Pro for Windows by Microkinetics on a mill/drill.

My software doesn't have tool radius compensation and I'm looking
for advice on how to approach programming toolpaths. I hope I can
explain this clearly. I'm finding calculating the cutter waypoints
tough.

Should I CENTER the spindle on the workpiece origin (0,0) or the
EDGE of the end mill on the workpiece origin 0,0? For example, let's
say I have a 1" x 1" (I'll ignore Z) workpiece with a 3/4" end
mill. If I set the center of the spindle (using absolute mode) on
0,0 (front left corner of workpiece), then I have to reposition the
spindle by -.375 in both X and Y or half the distance of the cutter
to get to the edge of the workpiece. The second way I could do it
is to move the cutter to X-.375 Y-3.75 and then initalize that point
as the origin (0,0).

Any suggestions on which way to approach this?

Many thanks,

George