Everybody is nervous at interviews so don’t worry about it. If it becomes a real problem, then go for a walk just before the interview and watch other people living their daily life – try to realize that if you fall the interview is not the end of the world. There are other more important things in life.
It is obvious that you are expected to arrive on time, but a surprising number of people still manage to arrive late and this clearly makes a very bad impression, however good the excuse is. If you do arrive early, you can always spend time looking around the premises. Decide if you would like to work there.
Even in this day and age it is still worth taking some trouble with your appearance, especially if you are going to an interview at a big multinational company or bank or insurance company. Put on your best clothes and make sure they are ironed. It is probably not a good idea to smoke during the interview -smoking has had such a bad press recently that is not worth taking the risk.
Be polite but do not necessarily accept everything they say - be prepared to challenge some of their ideas. Employers are always happy to have people who have clear ideas and express their opinions with some force.
Do find out as much as you can about the company or institution before you go. Find out exactly what they do and find out as much as you can about the job you are applying for. If you can’t find out certain things then make a note and ask them at the interview. Employers are always impressed when they find someone who has done their homework and someone with an enquiring mind - but plan your questions before you go. It is even worth writing them down on a piece of paper and looking at them again just before you go in. Finally find out the name of the person who is going to interview you.
Try to predict what questions they might ask you. It’s much easier to shine at an interview if you can answer questions quickly and efficiently.
Above all, show confidence. Tell them you are sure you can do the job and would enjoy the challenge and stimulation of working there.