[williecoyote]

When cutting crown moulding, I used to cut it backwards, and upside down. After awhile it takes much less thought, and then I sometimes cut it right side up. Take a short piece of crown, maybe 3" long, and "bed" it (make sure the bottom back edge is flat against the wall, then slide it upward until the top is touching the ceiling) then with a pencil lightly mark the wall at the base of the crown moulding. Do this at each corner of the wall that you are running, and every 24" or so between the corners. This will help you as you are nailing up your moulding to keep it straight, and not twist it (which would make the corners harder to match.)
On outside corners, let the outer 24" of moulding "float". (don't nail the 24" nearest the corner. Then when you run the piece around the corner, "float" the end of it too. Now grab one corner in each hand, and twist them up or down until they fit just right. At this point nail the one side off at the corner, and then the other. (Glue your outside corners.)
For inside corners cut the longer piece square, and butt it all the way into the corner. Again "float" the last 24" or so into the corner. (Remember the lines you made when you bedded the short piece of moulding, and marked the bottom on the wall. This will help to get your moulding in the right place.) Now for the coped piece. Measure all the way to the wall at the bottom of the crown. This is your dimension. Cut your moulding with an inside 45 degree angle. ( Long point will be at the bottom) Now take your coping saw and cut along the miter, removing the miter,and keeping the profile of the moulding. You want to slightly " back cut" the moulding so there is no wood remaining beyond the miter, which would cause a gap when you make your inside corner.
Now you have the square piece floating into the inside corner, and you want to pin it in place with the mitered piece. Again you will twist both pieces of moulding until the gap is closed. Nail the mitered piece in place. Do not nail the square piece in the corner, or it will open the gap which you worked so hard to prevent.
As mentioned earlier, make a few practice copes to get the hang of it. Keep a sharp blade on your coping saw. (They're cheap.)

Hope this makes sense