I just finished a "Yellow Brick Road" Quilt. Some tips that really helped make it nice are:
-use the number of fat quarters recommended. I made sure that for each color in my quilt (I used blues, wines and greens) I had light, medium and dark values of colors. This makes the final layout pleasing to the eye, gives movement and dimension.
-select a border fabric that incorporates all colors used in the quilt blocks. A nice border fabric can 'tie' the quilt together.
-Random placement does work! When I pieced my squares, I tried to piece both light and dark fabrics in the square....not making any square all darks or all lights, etc.
-When all squares are completed, lay them out on a bed or artist wall. Make sure no one piece of fabric touches one that is exactly the same. You should have a few quilt blocks left over, so you can switch in and out as you need to. I only had to change two of my blocks around.
-When you have made your final arrangement and are happy with it, step away and squint your eyes. You should see an even display of 'light' and 'darks' around your quilt, peppered with mediums. If you have too many 'lights" or "darks" in one area, rearrange until it's pleasing to the eye.
Good luck!
Romay