Enthusiasm

One thing I've noticed that seems to make a difference in a design is an enthusiasm for the subject. You can really tell when a designer cares about what they're working on, because there's just more energy in the project. There's more humor. There's small details that may not make a difference to a casual observer, but show a level of care and pride. I love it when that sense of ownership drives my process; it's when I do my best work.