Complimenting an aspect of a person's personality, such as telling your friend that he has a great sense of humor or that he's good at talking to new people, can make a person feel more special than a compliment about physical appearance.
If you're complimenting something physical, make sure it doesn't come off the wrong way. If you're complimenting somebody's appearance, stick to their face or hair and avoid complimenting their body or your comment may come off sounding more forward than you intended.