Facial expressions. Nothing more off-putting than seeing a skater look like they'd rather be anywhere else. It makes me think: 'If you don't give a shit about your own performance, why should I?' Performance skills in general as an extension but whilst not everybody can easily achieve a great posture, lines, etc. etc. it really doesn't take that much to show some kind of emotional involvement (yes, I know it's not easy if you're focusing on technical elements but still). Giving a shit about music is nice as well. You know sometimes a really little detail, like bobbing your head to a musical accent, can make a big difference.