You don't know squat about making tea

If you're lucky enough to be moved over here at some company's expense, they generally provide you some acculturation classes to help you integrate more smoothly. One of the classes given to Americans moving to the UK teaches you how to make tea. Really. There's such a thing as a “proper cup of British tea”, and Americans don't know a damn thing about making one. It may be hereditary from what I can see; my wife has a friend named Elizabeth who's from Mississippi and lives in Berkshire with her British husband, but although she's lived here in the UK since she attended Cambridge, her husband still doesn't allow her to make the tea. In her blog, Elizabeth writes:

There are so many rules on how to make a cup of tea correctly. One friend puts milk in straight after she puts the tea in but my husband declares this approach totally wrong. He puts a little boiling water in first, lets it brew, then tops it up and milk goes last.

I, for all the years I have lived here, have never learned to make a 'proper' cup of tea, and the stuff I make has no flavor. Therefore, whenever I see a British person near a kettle of boiling water, I make them make me a cup of tea because, as my husband says, I can't be trusted with this task.

When we moved back to Chicago after living here the first time, the movers came with their own electric kettle for making tea on their breaks, and it was pretty clear that they'd moved enough Americans that they knew that if they wanted a proper tea they'd have to take care of it themselves. Therefore, Americans visiting here should just give in and leave the tea-making to the experts. And don't even mention sun tea.

Americans sound stupid using British colloquialisms

Really stupid.

So don't come here thinking you can say “cheers”, “quid”, “crikey”, or “mate”. You might get away with “oi” since it's close enough to “hey” that people might not be sure what you said. We've struck a diplomatic accord with our friends that if we don't say “quid” they won't say “buck”. One exception is “no worries” since that seems to have been appropriated from the Aussies anyway. But in general, resist the temptation or risk being considered a wanker.

You think you know English? You don't know English.

Compared to the British, Americans are newbie English users. In British hands, the English language is a tool of infinite subtlety. For example, when a Brit tells you that they “agree with you to a point”, this doesn't mean that, with the exception of a few aspects, agreement has been reached; it means they don't agree with you at all. The magazine The Economist once reported that English-speaking Dutch diplomats had to employ British translators in order to understand what their British counterparts were really saying. This adds a whole new dimension to arguments at the pub.