New designers often want to skip sketching. They want to jump into the exciting part—the real design. They want to get something built. But sketches are important because they prevent you from committing to a solution too soon. If you jump into creating a polished, detailed version of the concept before you are certain it’s correct, that’s a risk. Better to spend 15 minutes sketching to ensure that time won’t be wasted by having to start over.

You might think sketching is a bad idea unless you have some drawing skill. … many designers’ sketches look like works of art, but yours shouldn’t. Your sketches should be quick and ugly. The only purpose of these sketches is to explore ideas quickly. The more beautiful your sketches, the more time you wasted. Let them be ugly.

Jarrod Drysdale.