What cultural faux pas should I try to avoid making in Wash DC?

We asked people in Wash DC if they could share any humorous cultural blunders they commited. For new expats, keep in mind that these incidents are an inevitable part of expat life. Learning to laugh about them is the key!...

Other Questions:

•  What should I pack when moving to Wash DC?
•  Where should I setup a bank account in Wash DC?
•  Will I be able to find a job in Wash DC?
•  What is life like in Wash DC?
•  What do expats in Wash DC appreciate most about the local culture?
•  What do expats find most challenging?
•  Is there a lot of crime in Wash DC?
•  Is there a lot of diversity? Are people in Wash DC accepting of differences?
•  What are the schools in Wash DC like?
•  What are healthcare services like in Wash DC?
•  What are medical services in Wash DC like?
•  Are healthcare and health insurance expensive in Wash DC?
•  What are emergency services like in Wash DC?
•  Will I need to travel to see a specialist?
•  Are common prescription medications available in Wash DC?
•  How are local medical facilities in Wash DC?
•  As a foreigner living in Wash DC, will I have access to public healthcare? What is it like?
•  What have your experiences during the pandemic with the local healthcare system been like?