Typically, if there is no Coordinate System indicated, a local datum is used. When i draw those, I look for statements in the legal description that indicate what the local datum might be. This could be, for example:
Commencing at the southeat corner of Soandso's Addition, as the same is platted and recorded in the office of the Recorder,
Thence North 00°36'00" East a distance of 827.88 feet, on an assumed bearing on the east line of said Soandso's Addition, to the northeast corner thereof.
So in this case, you would know that the description is based on Soandso's Third Addition, specifically the east line of said addition. Now you would use the COGO Report tool or some other means to identify the bearing of that north line in your current coordinate system. In this example, let's say I get a result of N 00°27'58"E. This is that line they are using as the local datum, but in the coordinate system your map uses.
New, open the Ground to Grid Correction tool. Here, check Use Ground to Grid Correction, and click the pointer tool under Enter the ground line and click on the map for the grid line. In the window that opens, enter the bearing from the legal (North 00°36'00" East) using the ArcGIS bearing notation and leave distance along, unless you have a reason to change it. This would apply a constant distance factor.
Click OK, now click the beginning and end points of the line that is used as the reference, just like you did with the COGO Report tool to measure it.
The result should indicate a Direction Offset of 0-8-9 and distance offset of 1 (stays the same).
Click apply, now enter the metes and bounds like you normally would, and ArcGIS does all the tranformations to the local reference datum for you.
Don;t forget to deactivate Ground to Grid Correction again when you're done.
Now, after drawing your line, of you use the COGO Report, it will indicate both a Ground and a Grid bearing. Ground bearing is the bearing in the local datum used in your description, ground bearing is the one used in your map.