You are an unknown seeking to make a good impression to somebody who cares deeply about what you're after, be that a place at a company, or a beloved son or daughter. The paths through both of these situations are riddled with danger, but in each there are cardinal sins: things you should not on any account say or do.
Let's start with the obvious:
Badmouthing your last employer is clearly going to get you nowhere.
Pitch up at your new love's house for dinner and spend the whole time telling the potential in-laws in minute detail the flaws of your ex isn't just creepy: it shows you're untrustworthy. A job interview is scarcely different; complain about your last post to your interviewer and you will come across as disloyal and quite probably exactly the sort of difficult employee they're trying to avoid. Of course, it's not impossible that the more intense interviewer will ask why you wanted to leave your last job. The best policy in this case is surely to place more emphasis on the pulling power of the new role than what repelled you from the last one: 'I really like your daughter' sounds a lot better than 'the last one didn't meet my standards.'
And then there's that awkward section in the interrogation: your hobbies. There are faux pas to be avoided here too.
Telling an interview that you enjoy 'an active social life' has never seemed anything but euphemistic.
You probably wouldn't tell your girlfriend's parents just how much you love partying, and neither should you tell your employers. Sports, culture, literature - fine, but toe the line. Originality can be a bonus, but it's best to err on the side of caution. Extolling the virtues of Fifty Shades of Grey might help them remember you, but probably not in a good way. Equally, something a little quirky might seem fresh, but a raised eyebrow is not always a sign of success.
Probably the most dangerous pitfall, though, is the thorny area of money, holidays and benefits.
Often the curious candidate can't resist the temptation to ask; but really, the 'do you have any questions for us' section is best used to subtly show off your knowledge of the employer, whilst appearing interested to know more. Remember always that it is they that hold the power of rejection over you. Asking what they can offer you rather turns the interview on its head. Likewise, you wouldn't ask your partner's dad on first meeting him whether you can go and help yourself to what's in the fridge.
Remember your humility, avoid criticising past employers and try to steer a path between coming across as a complete lunatic and a total dullard, and you ought to be fine. The task then is to prove how good you really are.
Tom, GRB Journalist