Preparation
Time spent preparing for the interview will really pay off on the day, provided that the information you collect is used in the most effective manner.

Find out all you can about the organisation, in particular ensure you have found out the following:

Who owns the organisation?  Is it part of a larger group or does it have subsidiaries? 
Turnover and profitability
Competitors, market rating
Future plans for development

Useful company information can be found from the library or via the internet, especially from their website.

As you read through the information write down any questions which come to mind.  It is vital that you have a good selection of pre-determined questions.

Remember to ARRIVE EARLY.  Research the location prior to the interview, so as to avoid arriving late.

Smart dress is of a pre-requisite.

Interview Technique
Listen to what the interviewer is asking.  Answer clearly and concisely and if you are unsure of what is being asked, clarify with the interviewer what information he/she is seeking.  If at any point you begin to have reservations about the position, do not show it.  Never shut out the opportunity.  You never know what opportunities may come up in the future within the same organisation.

Many questions can be anticipated in advance and it is wise to prepare the answers in advance.

Frequently asked questions include:

Why are you seeking new employment?
What are your strengths and weaknesses?
What sort or salary are you looking for?
What attracted you to this organisation?
What is your main achievement?
Describe your management style?
What do you know about the company and why do you think you are a suitable candidate?

Asking Questions
Whilst it is important to ask questions, you should be careful not to end up interviewing the interviewer.

Consider asking the following questions:

How will my performance be assessed?
What are the longer-term opportunities for promotion?
How did the position become vacant?
Is encouragement give to undertake further training?
How does the department integrate with the rest of the organisation?
What is the strategic plan for the company?
What would you like to change about the company?
Where do you think are the teams strengths or weaknesses?
What is your management style?
How do you think I would fit into the team and the company?

Closing the Interview
Always allow plenty of time to see the interview through.

If you are asked about your continued interest, remain positive.  Give yourself time to reflect and think about this position.

Establish what the next step will be.

Make notes/comments about the interview the same date there may be a delay before the next stage and this will help to clarify points in your mind.

If you are unsuccessful in getting the job, find out why – once you get feedback you can address the problem if there is one.