This tip came to me while working with Cogo points in Civil 3D, but it could apply to many things. A while back I had a tip about setting PICKADD to 0. Now generally, this system variable set being to 0 would annoy most people since it only allows you to select one object at a time. But if you are working with Civil 3D Cogo points, say for example dragging labels to create a dragged state, and you are doing this over and over, setting PICKADD to 0 can be a big help. Doing so means you do not have to press Escape to clear the previous selection. As soon as you pick one point, it is selected and all other selections are cleared.
Remember to turn OFF the Properties Palette when working with Cogo points. If the Properties palette is on, Civil 3D has to look up and display the properties each time a new point (or points) is selected and this slows it down tremendously. Try it both ways and see if you see a difference.
For some reason lately, I have been running into an obscure system variable that is wrecking havoc on certain AutoCAD commands, or so it may seem. Some of you may have heard of QAFLAGS. I first ran across it years ago at manusoft.com, where Owen has provided documentation (not sure if that is his own description, or something originally from Autodesk...). The default value is 0. I've been using it for years to bypass the pause in text screen listings (bitcode 2).
Note that because it is a bitcoded system variable, you can set it to any valid value such as 384 (128+256), 1538 (1024+512+2), 32767, etc., however the effects of these other bits are undocumented, if they do anything at all.