I have always been interested in decorating and design and choosing quilt fabrics came easy to me I think because of that. One thing I remembered from decorating books was how to mix patterns and that applies just as well to quilts. a quilt with one bold print and all the rest solids or tone on tones can be boring. On the other hand, two or more bold or big prints in a quilt can fight each other and not play well together. But a large bold print, a small floral, a plaid or stripe in the same colors, as well as a couple tone on tones or solids can blend beautifully. And contrast is important too. All darks would be a little dreary, and all lights kinda fades away. You may not want a wide contrast going from very light to very dark, but having some is important. Even in a pastel quilt, having some medium tones to add to the lights makes a much more interesting and striking quilt. And I read something once about using one color in scrappy quilts, which I love to do - vary the tones of that color on both sides of the color wheel. For instance, if making a scrappy blue quilt, add blues that have a purple tint and blues that have a green tint as well as true blues. Since I started doing that, my scrappy quilts have become a lot more vibrant.