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Hi,
You can treat one AutoCAD unit as one meter in real world. That is all you need for drafting purposes.
Another thing is adding annotations and dimensions to the drawings and output itto hardcopy (or to PDF). There you need to setup output scaling and the size of annotation objects (text, dimensions, symbols, etc.)
You can output from Model space or from Layout.
In Layout (which usually have the dimensions of real world paper sheet) you create viewports to Model space and set the desired scale in order to present your drawing correctly.
If you would output from Model space, you need to adjust the size of annotation objects depending on the scale at which you want to print the drawing.
BTW, the best practice is to assign one AutoCAD unit to one millimeter in the real world, than it will be easier to calculate scales and the size of annotation objects.


Maxim