Put it down to nerves, or inexperience, but plenty of people answer interview questions badly. Take the male candidate who mentioned his sexual prowess when asked to describe the achievement he was most proud of. Or the person who described the rigours of enticing pigs to mate when asked to provide an example of his persuasiveness.

'It's surprising how un-clued up people can be about what we're looking for,' says the head of graduate recruitment at one investment bank. 'At graduate level, answers can be really outrageous.'

Some mistakes are self-evident. Angela Garnett, head of graduate recruitment at Lazard in London, recalls one candidate who was asked if he read the financial press said he found it quite boring. 'It wasn't a good answer,' Garnett says.

Round one: examples, examples, examples

Just what are banks looking for? Examples, is the short answer. Most of them use 'competency based' interview techniques.

In the first round of interviews in particular, candidates are typically asked to provide examples of situations in which they have displayed a particular competency (skill or behaviour).

'We look for specific examples of past behaviours which provide examples of future potential,' says Nancy Labiner, head of Europe campus recruiting at Goldman Sachs. 'We don't require investment banking experience: a candidate can talk about a job at Starbucks if they can tie the experience to leadership, working as part of a team or dealing with difficult customers, for example.'

First round interviews are typically conducted by junior bankers and graduate recruitment staff. At this stage especially, you will need to stand out: a bank hiring 200 graduate trainees will interview around 1,600 people at this stage.

What do banks want?

When it comes to behaviors, most banks are keen on the same things. These include the following:

• Team building
• Communication skills
• Pro-activeness
• Assertiveness
• Leadership skills

Joanne Scott, head of resourcing at Morgan Stanley, says questions designed to elicit desired behaviors might include, 'Give an example of a situation when you demonstrated leadership', or 'How would your friends describe you?'

Questions are designed to be open-ended, says Scott. Within reason, responses can cover any subject area, as long as they are detailed and specific to the candidate replying. 'It's no use talking about leadership in terms of 'we',' she advises.

Round two: brain teasers

If first round interviews are about checking a candidate has the right behavior, second and third round interviews are more technical. At this stage, interviews are more frequently conducted by senior bankers.

'Some businesspeople like asking bizarre questions and conducting high pressure interviews,' says Vivienne Dykstra, former head of graduate recruitment at Deutsche Bank and now a consultant on graduate recruitment techniques. 'The idea is to put candidates on the spot and grill them until they crack, with a view to seeing how they react under pressure.'

Dykstra said a favored conundrum is, 'Why are manhole covers round?' Answer: 'So they don't fall down the hole, and can be rolled along instead of lifted.' Others have been known to include 'How many red cars are there in the U.S,?' or 'You have a bowl of 100 marbles, 50 are black and 50 are white. Devise a strategy for being able to separate them when blindfolded.'

David Schwartz, a financial services headhunter at Highland Partners in New York, and former global head of campus recruiting at Goldman Sachs, said high pressure interviews are increasingly frowned upon. 'HR people have to restrain bankers from asking these questions. In the end, a guy who knows how to solve a brain teaser won't necessarily be any good at bringing in a corporate finance deal.'

Candidates bite back

One recruiter tells an anecdote about a candidate who, tired of being bombarded by brain teasers, chose to turn the tables on his three questioners. 'Assume there is an investment bank where a third of employees are asses,' he is said to have asked. 'What is the probability of any three interviewers also being asses?'

Needless to say, he didn't get the job. However, interview glitches don't always spell the end of a candidate's chances. At the end of one successful interview, Dykstra says she asked an interviewee what he could say to recommend his candidacy: 'I haven't got a criminal record,' he replied. He went on to become a successful trader.

Sample interview questions:

For examples of behavioural and sector specific questions at Morgan Stanley visit http://www.morganstanley.com/careers/recruiting/interview/intq_na.html.

Sample brain teaser questions used by banking interviewers:

Q. At dawn on Monday a snail fell into a bucket that was 12 inches deep. During the day it climbed up 3 inches. During the night it fell back 2 inches. On what day did the snail finally manage to climb out of the bucket?

A. The following Wednesday, nine days later.

Q: A man drove from Aardvark to Beeville. On the first day he travelled 1/3 of the distance. On the second he travelled 1/2 of the remaining distance. On the third he travelled 2/3 of the remaining distance. On the fourth day, after covering 3/4 of the remaining distance, he was still 5 miles away from Beeville. How many miles had he covered so far?

A. 175 miles: the total trip is 180 miles. On the first day he travelled 60 miles, leaving 120 miles. On day two he travelled another 60 miles, leaving 60 miles. On day three he travelled 40 miles, leaving 20 miles. On day four he travelled 15 miles, leaving 5 miles.