I've been working with AutoCAD since '87 and I have never found a use for grid and snap.  I think the best way to be very precise with input is to make sure ortho is on then pick line, pick a starting point (osnap is good for this), move the mouse in the direction you want, type in the distance for the line and hit enter.  Angles can be typed in by using the @2.666<45 format.  Sorry I'm not much help with what you were asking but maybe this will help.

Edited by Ron C - 14.Oct.2009 at 19:28

I. Viera

I find it very useful to have my drawings originate at 0,0,0.

When I want to move my drawing so that it matches the grid and or the 0,0,0, I select all then

1. set my snap to 1 or 2 inches
2. turn off snap,
3. turn on object snap
4. select the point in the drawing that I want to relocate to 0,0,0
5. turn off object snap
6. turn on snaps
7. move my drawing to 0,0,0
8. Return to you old settings

Maybe there is a function for this but I have not found it.

Barry