Usage patterns
外見で〈人〉を判断するto judge someone by their appearance
You shouldn't judge people by their appearance.
外見を気にするto be concerned about one's appearance
He is very concerned about his appearance.
外見にこだわるto be particular about one's appearance
Young people these days tend to be particular about their appearance.
外見が変わるfor one's appearance to change
His appearance changed a lot after he changed his hairstyle.