Definitely agree about greeting shopkeepers; this applies to most places in Europe and beyond. It may be less essential in a large chain store; you don't have to walk out of your way to greet the supermarket checker who's scanning another customer's items. But if you walk into a small shop within sight of an employee, definitely say hello and goodbye/thank you.

So far I've never been anywhere in Europe that I couldn't get by not knowing much beyond English (even in Macedonia, when the airline lost my luggage). However, anywhere you go, it's always good to know at least 6 things:

- yes
- no
- hello
- goodbye
- please
- thank you

That alone will get you far, even if only to appear like you're trying. It's also helpful to know "Do you speak English?" and "I'm sorry, I don't speak/understand <local language>."

My personal Paris story: my first time there, the person who ended up coming across rude was, accidentally, me. I was arriving on a TGV train to Gare de Lyon and leaving on the Eurostar from Gare du Nord. I had a short connection time to figure out how to transfer on the RER, so as the train was pulling into the station, I grabbed my luggage and headed for the door. A woman said something to me in French - it could have been "what's your hurry, take your time and enjoy life!" or "are you lost? can I help you get somewhere?" or even "you Americans smell of elderberries". I wasn't expecting to have to converse with anyone during this short period of time and, somewhat flustered, I blurted out "je ne parl pas francais" in a way that I think came across as "I don't bother with your %@#! language." I at least prefix that with "pardon" now.