How big to make the model in milkshape

#1 Jim, sort of a guess and test thing and I have even tried to make my model huge, it came out the size of an ant. Eventually you'll need to test it out, but for the time being you can adjust the scale of the object. That's probably the easiest thing to do right now.

#2 I was going to ask this same question except I am using blender and not milkshape.

Don't models have some kind of size value associated to them, like images do with pixels?

I even downloaded the ShowTool demo to see what my models looked like in that, and it does allow you to get a visual relative size compared to the grid, but this still involves alot of guesstimating etc...
Also, given that say i make a model too large, rather than resize/scale it in the 3d program, are there values that can be modified in the .cs files that will size it properly?

#3 In Milkshape3D, one UNIT = one TGE meter, so the default player character, whichi is ~2.4 TGE meters tall, would be 2.4 units in Milkshape3D. That's very small. If you scalled objects natively in Milkshape to that config; you'll get things looking good in TGE without a lot of back/forth scaling in the modeling apps...or dynamically by the engine.

Can't speak for Blender; and GameSpace[which I also hold a license for] can set units at will as does Max, so it's moot for those. If you wanted to work in Milkshape at a larger scale, you can set the exporter's Scale and do it during export process.

#4 For gamespace/truespace, you need to normalize the size first - there's a plugin lying around somewhere for it...