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

We asked people in California 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 do I need to know before moving to California?
•  How do I find a place to live in California?
•  What is a typical expat home or apartment like in California?
•  What is the average cost of housing in California?
•  Should I buy or rent a home in California?
•  What should I pack when moving to California?
•  What cultural faux pas should I try to avoid making in California?
•  Why do people move to California?
•  What are healthcare services like in California?
•  What are medical services in California like?
•  What are typical rents in California?
•  What appliances are typically included in a rental?