I'm a contractor: 6 months here, 3 months there... So I interview all the time:
tips
The CV can be more important than the interview. Have a good one.
look at the books! I know for a fact I've passed interviews by reading them. They are in your library or book shop.
Practice interview.
If you've time; apply for jobs you don't want, to get the practice.
Go in plenty of time.
All clean clothes, shower and mints.
Keep your hands on your thighs while you are waiting and you can rub them dry as you stand up to greet them.
Start with a joke mildly at your own expense. If they'll ask you how you got here say 'even i didn't manage to get lost'. That should be the last negative thing you say about yourself. They may only remember the negative comment if you do.
You should conrol the pace of the interview. Speak slowly and answer when you are ready.
Have answers ready for these questions
Why do you want this job?
What do you have to offer?
Where do you see yourself in 5 years time?
How would you deal with the situation where your child has just been in an accident and has an hour to live but we want you here?
How do you deal with obnoxious/lazy/dirty colleagues.
What are your strenghts?
What are your weaknesses? The answer should be 'I'm too keen on doing a good job and can forget sometimes perfection isn't needed'.
How do you deal with a problem you just can't solve?

At the end of the interview ask 'Are there any areas of this role you are concerned I might not be able to handle?' This gives you a chance to address that area again or confirm to them you can do the job.
If you don't get the job; write them a polite note saying it was nice to meet them and thanking them for the interview. Then remind them you are still available immediately. Then if the other fellow doesn't work out or turn up they'll know they have a replacement handy. (I've got a job a few times with this one).
There is a proven correlation between nodding eye and eye contact in an interview and the chances of getting it.
Above all remember; PRACTICE INTERVIEW.
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