Speaking a foreign language badly, not knowing a word for something, or only knowing the most basic greetings. People all over the world are generally delighted that you bothered at all, and are eager to teach you more. This has been true for me in big cities (even Paris) and tiny villages. The more obscure the language, the more delighted they will be. I have botched so many languages and conversations with strangers at this point that I am immune from embarrassment about it.