When visiting London one should remember to use an "indoor voice" while travelling on public transport, and it's also a good idea not to make eye contact with anyone at such times for fear of being too invasive.
These are essentials and possibles covered in a rather meticulous guide for tourists coming to the capital, released by Condé Nast Traveler.
Tourists looking to fit in during their visit to London should observe staunch standards of British politeness, states the guide.
"British people are generally very polite. Always make sure you greet with 'good morning,' 'good afternoon,' and 'good evening' when entering a shop/restaurant; or just drop the 'good' for a more casual greeting."
Dropping the 'good' - a staggeringly informal suggestion. Be warm and friendly, the article continues (but not too friendly; don't hug anyone, for instance).
"Saying 'How do you do?' will really make you stand out," it states. This is undoubtedly the truth.
Regarding the volume of your speech, take note that Londoners are not loud speakers, "despite the impression given by many a taxi driver".
On the thorny issue of British greeting protocols, the article is to some degree equivocal:
"There are no hard and fast rules for whether you should shake hands, hug or kiss someone when you meet them in London, which could account for the notorious awkwardness of British greetings.
"A handshake is a safe, if slightly formal, bet. A hug is acceptable if it's a friend of a friend, but not a complete stranger. Going in for a cheek kiss as you would on the continent will probably end in embarrassment."
A list of dos and don'ts includes the following:
Do Wear a hat. The weather is very variable, and hats will protect you from rain, sun and wind while giving you a touch of style and Britishness.
Don't bother carrying an umbrella. Opt for a trench coat and a hat, or simply a copy of today's newspaper.
Don't make eye contact on public transport. Londoners are infamously evasive when it comes to being crammed inside a crowded bus or tube train.
It will come as a relief to many to know that in London you can have tea at any time, and depending on the kind of accompaniment you get, you may or may not want to have another meal afterwards.
If you want to blend in then avoid at all costs the likes of Madame Tussauds, the London Eye and Oxford Street - Londoners avoid these touristy spots like the plague, the guide informs.
Try an independent book shop in Marylebone instead. Or opt for a market. "Londoners love a market, especially at the weekend."
If you want to be in fashion, relaxed yet stylish is the way to go: "If you can't afford a Burberry or Aquascutum trenchcoat, invest in a well-structured, non-slouchy one, which will go with everything."
American visitors should remember to not to ask for pants unless they are looking for underwear.
"When shopping for clothes you should ask for trousers, and jumpers instead of sweaters. Since they seem to be back in style, the word 'fanny-pack' is a big no-no in British English. You can ask for a waist wallet, or a bum bag instead."