I'm no expert but I've developed a few strategies for doing this. The procedure depends on the precision that I need. I work on the PC in Freehand 8, so you will have to adjust for other versions.
Before begining, you need to understand the properties of complex (rounded or beveled) corners, points, and handles.
Gradule corners can be made by stretching handles between two points. Taking that to its limit so that the handles touch or cross each other makes the corner sharper or even convoluted. In this manner the line leading into the corner is actually a spiral (has a constantly changing radius).
You can quickly stretch two handles into a line segment by holding down the alt key and pulling the segment with the cursor in the direction that you want the line to curve. The points defining the segment don't have to be selected in order to do this. Don't click on the points or you will only pull out a handle from the point itself.
To make more accurate rounded corners you can do as the program does for squares and regular polygons with rounded corners. Simply define two points close together for each corner then pull acurve between them such that each of the handles are simultaneously aligned with the line segments on the opposite side of the point attached to the handle.
Alternatively, for even more accuracy use the object editor.
define 2 point corners, select all the points including the ends, click on the corner point button in the object editor (this puts handles on everything and makes all the lines curved), select each point one at a time, then pull the handle leading to or from the double point to the other point at the extreme far end of that line segment, and then delete the handle that you just pulled out using the retract handle button in the object editor. (When you pull the handle to the other end you are actually aligning the handle between the double points. You don't really neet that other handle so delete it to keep it from messing up the line segment between the double points.)
For the most accurate curved corner with single points defined use cut and paste.
-Define a small circle having a radius that is the size you want for your corner radius. (clone it for as many points as you need to alter)
-Move each circle to the point it will alter.
-Go to a high magnification and put the circle on the lines next the point so that the lines are tangents that align with the circle. (use keyline view to get this exactly on)
-select both the circle and the line than cut across both the intersections.
-delete the unwanted pieces then highlight and join each end of the arc cut from the circle to the line segment that it touches.
Hope this is useful.
