I recently purchases a set of top down bottom up shades from CellularWindowShades.com. I had some issues at first leveling the top down bottom up aspect of the shades, but I found an easy trick that might be helpful for others.
Step 1: Stack the Shade
You want to stack the shade and its fabric so that it rests a few inches below the top rail. It needs to be 100% compressed and closed.
Step 2: Make Sure the Shade Is Locked in Place
This is simple, just make sure the strings are locked so the fabric doesn't fall.
Step 3: Firmly Grasp the Shade in Two Hands
Gently tug the part that isn't level to ensure that both parts are level. I believe the brand of shade's I own are self leveling. If your shades do not have this self leveling feature, this instructable will not work for you.