While the worksheets included in Libs' instructions are definitely helpful in figuring out your colors and layout, if you don't already have one now might be a great time to consider a design wall. This will allow you to layout your ideas full size and move things around to find a design you really like. It is a really useful tool to have both when you have a set pattern you are following, like the Weight of Love quilt, but need to decide on the color layout and when you are experimenting with an idea and want to see how it looks different ways before sewing everything together.
You can make them as simple or as complicated, as big or as small, as movable or as permanent as suits you. My work space is fairly small, but I did manage to clear some wall space and simply hung a vinyl tablecloth, right side facing the wall, so that the fuzzy underside faces out. You could also use a flat flannel sheet or a piece of cotton batting; they even make flannel fabric with a grid printed on it. If you don't have the wall space to spare, wrap that flannel or batting around a piece of heavy cardboard, wood or foam core that can be stored away in a closet or under a bed when not in use.
For some inspiration on how to make a design wall that suits your workspace, you can check out our Design Wall board over on Pinterest, or check out one of the tutorials below. They offer a wide range of size, price and permanence which is great for those of us with limited time/space/money! ;) Also, if you have some tips or tricks to share on making a design wall, leave them in the comments!