Here are some actions you can take to help improve your impression:-
ARRIVAL
Few things give a worse impression than turning up late. Allow yourself plenty of time, ideally arrive 10 minutes early and if unfamiliar with location do a dry run. Wait patiently, be courteous and professional to everyone you meet, you never know how much influence the receptionist may have on the hiring decision.
INTRODUCTION
When you first meet your interviewer try to make a strong first impression, make eye contact, be positive, talk confidently, say your name slowly and clearly. When shaking hands, match the pressure of their handshake...do not be a limp lettuce or wet fish.