Although I've seen total scrappy quilts, for instance postage stamp quilts, that I thought were totally stunning, I gravitate more to the controlled scrappy camp. As others mentioned, a single fabric unifying sashing does wonders. I also like the ones where all the lights (or darks) are just a couple fabrics very close in color and value rather than just lighter or darker than the adjoining fabric. Choosing a pattern that uses lights, mediums & darks also helps keeping things lively.