It took me a long time to realize the joy of using the Control and Shift keys when dealing with Windows. Apparently, it's taken me just a bit longer to realize all that the SHIFT key can do in AutoCAD.
1. SHIFT + LEFT mouse button: Will remove objects from your selection set, if you're selecting objects before issuing the command. ie, Select objects and then invoke COPY.
2. SHIFT + RIGHT mouse button: Brings up the OSNAP menu during many commands, as long as you have the RIGHT click option set up correctly in OPTIONS > USER PREFERNCES.
3. As we mentioned in an earlier post, if you want to FILLET or CHAMFER with a 0 distance, and not have to reset your radius or distance, you can:
Pick your first line.
Hold down the SHIFT key and pick the second line.
This will fillet (or chamfer) with zero radius without changing the preset fillet radius.
4. You can also hold down the SHIFT key while using TRIM or EXTEND and it will perform the opposite command.
Select TRIM and choose the line to trim back to.
Trim several lines.
Hold down the SHIFT key and pick a line and they will EXTEND to the trim line.
5. SHIFT + WHEEL/MIDDLE mouse button will start a 3D Orbit around your model as you move your mouse.