If a man is balding, it might do to put a little baby powder on to eliminate the shine. You want to look good. You don't want highlights from jewelry, etc. Don't talk directly to the camera unless you are asked to do so. Talk to the interviewer, or in a panel situation, to the person you mean to address.
Eye contact is important.
Darting glances come off as untrustworthy. If you can't look at a person, pick something to focus on. If you are passionate about your message, just tell it and try to convince the person talking with you. Gestures are fine for emphasis. Don't be threatening, however.