Do you bow, curtsey or ignore an oriental potentate? Do you look them in the eye or avert your gaze?
Not questions that are posed for most of us every day, but certainly the kind of thing that Kate Middleton is having to contemplate as she prepares to become Princess Catherine.
Prince William's bride-to-be is reportedly on a full etiquette and manners course designed to equip her for the royal life. It's the little things that make all the difference. A curtsey is not just a curtsey. Not enough knee movement and the foreign royal might be insulted - too much and they could be shocked - not to mention all the courtiers looking on from behind.
Even a handshake can cause offence if wrongly - dare I say it - handled. Too firm and with too much eye contact could cause a diplomatic incident. Too weak and deferential could mean a blow to national prestige.
One of the golden rules for Kate is to keep her knees together when sitting down. This rule must however be relaxed when standing up - otherwise it gives the impression of disability or worse - incontinence.
Kate will be sitting through thousands of banquets as a princess. And it is not down to whether she can balance her peas on her knife. The opportunities for mortal embarrassment and loss of face are manifold.
Wrong glass, wrong knife, wrong spoon, wrong fork - all can mean disaster. It is no good relying on the waiters and in most cases the host will be too polite to say anything. But that doesn't stop them thinking.
And if served up with a bulging sheep's eye, Kate will have to know how to tackle it. Winking back at it isn't enough.
And one more thing - if she's handed a bunch of grapes she must not be tempted to pluck one out. She should ask for the grape scissors and extract her own mini-bunch.
