I'd say the most helpful tip was to use the same ruler (or at least type of ruler, like "Omnigrid) to cut out an entire quilt because the little differences in rulers really do make a major difference when you want your quilting squares to all come out the same size, and thus your quilt matches up and is much easier to assemble. Use the same ruler, cut it correctly, use a scant 1/4" seam, and there isn't a lot else you can mess up.