Graph-paper plans. You can use graph paper to help determine the ideał depth of your border. In this example, each of the light pink rectangles is the same size.
Yarn weight affects scalę. The same edging mtked In baby-weight (teft), and chunky-weight (ńght) yams yields quite different results, as you can see In these examples.
Colorways. The same border can look quite different when you change colors. While entire books have been written on color theory, you can learn a lot by simply experimenting to see which color arrangements look best on a particular project.