Tip 3.
If the Mtext in the Mtext editor (2005+) is too small, or too large, hold the ctrl buttom and scroll the mouse wheel to change it's size. This only changes the displayed size in the editor window, and does not affect the object size. nor does the editor window retain the size of text you like to read, unless you changes the system variable MTEXTFIXED (0 = open sized and places beased on the mtext selected; 1 = fixed editor size and location)

Tip 4.
You cannot select entiries on Defpoints layer if layer 0 (zero) is frozen or turned off. You can still see the entites on defpoints, but you can't do anything to them. I look forward to seeing some tips from others.

Tip 5.
This is helpful if you use hatches. All hatches are inserted with their base point at 0,0. Even though you can't see it. Sometimes this can result in less than useful or incorrect (as in brick hatches in building elevations) hatches. You can move the "insertion" point by typing "snapbase" and then selecting a new point, like a hatch boundary point. Then insert your hatch.