Watch fiddling with your hair. Watch nervous hands. Don't lean back, cross your arms, or bow your head frequently. Look interested when seated by leaning slightly forward with the small of your back against the chair. You'll look open and honest.
More earnest honesty is communicated by upturned, open palms.
Half-glasses may suggest haughtiness. Keep your hands away from your mouth. You'll seem thoughtful and unflappable. You'll be seen as one who covers all the bases. Just don't make the mistake of holding onto your notes like they're a life preserver.