You want to be remembered as the self-confident candidate.
Consider the following:

It's not the time to make a fashion statement, so dress professionally.

Arrive before the scheduled time of your interview (but not too early).

Spit out the gum and kill the cigarette.

Be nice to the assistant.

Shake hands (firm, but not bone-crushing) as you meet.

Sit with erect posture, facing the interviewer, and make eye contact.