A job interview is one of the most stressful experiences there is - and it's not helped by the current trend for asking candidates questions for which it's quite impossible to prepare.
Sometimes, these questions are designed to reveal the personality of the applicant and get them chatting comfortably: "Which magic power would you like to have?", asked at Topshop, for example.
Sometimes, the aim is to discover whether candidates can think on their feet: "How many hours would it take to clean every single window in London?" IBM has asked.
All you can really do to prepare for such questions is to be aware that something like this may come up, and remember that it won't be pass-or-fail.
The interviewers will be interested in your logic. For example, if you're asked how many babies' nappies are used in the UK every year, as applicants have been at Aviva Investors, take a moment to think through the problem. It's a fairly basic calculation - the number of babies in nappies in the UK, multiplied by the number of nappies a baby uses per day.
Even if you don't know either of these numbers, you should be able to make a reasonable guess; and the interviewers will be looking at your reasoning and your confidence, rather than your knowledge of Pampers' sales figures.
"It's also about what your body language says about you. Employers are looking for those non-verbal cues to indicate a candidate's level of professionalism and if they will be the right fit for the position."
But while these off-the-wall questions are hard to prepare for, there are plenty of other things you can usefully do to make sure you're not caught on the hop.
Jobs website Glassdoor has a list of the top 50 questions asked at interview, and most of them are just what you'd expect - meaning there's no excuse for not having an answer prepared.
The most commonly-asked two are about your strengths and weaknesses, with the third being why you want to work at that particular company. And while the truth may be "The Jobcentre told me to apply," you'll need to do a bit better than that.
While the question is apparently about what you expect to get out of the job, you should make sure your answer describes what you could do for the company, says workplace culture consultant Steve Langerud on the Monster blog.
"Drill down on a key skill or deliverable that the employer needs and that you love to do," he says. "It is less important to the employer that you will love working there than the fact that you will get juiced by helping them improve their performance."
It's worth looking at the list and practising answers to any that you think might come up.
But you'll be expected to have your own questions for the interviewer too - something many candidates have difficulty with. Experts say you should try and avoid simply asking about pay and conditions, although asking about opportunities for career progression shows ambition.
Do a bit of research on the company beforehand, checking online news results as well as the company's own website: this can give you, for example, the chance to ask about expansion plans or other changes in the company's business.
It's also worth checking out the competition and the industry as a whole to make yourself look as knowledgeable as possible.
But your questions should also reflect what's gone on during the interview: make sure you have a pen and paper with you, and jot down anything that you'd like to follow up on as you go along. This will show you're sharp and on the ball.
While a job interview isn't a fashion show, it's also important to give some thought to what you wear. This doesn't necessarily mean wearing a suit, but it does mean being clean and well-presented.
The best tip is to try and find out what most people wear at the company, and aiming to be just a bit smarter. Avoid wearing a brand-new outfit, as you want to feel as comfortable and relaxed as possible - if you have bought something new, try wearing it at home for a day first.
Finally, make sure you arrive in good time. Check out your route first, and build in a little extra time to be on the safe side. Google will tell you if there's a cafe nearby where you can wait out any spare time. While it's professional to arrive five minutes early, you don't want to turn up too soon, as this can make the interviewer feel pressured.