Agree with most of your points. You have the sensitivity to learn new culture. Try to avoid using racial and sensitive words like '本地的白人'老外 etc, despite using it for positive or negative comments. Try not to describe a person starting with their racial features and country of origin. Start describe a person like 'a middle aged man', rather than 'a white man'.
I have been thinking of writing this kind of stuff for a long long time. But never start. Because, first, no time, second, I don't like rude comments and rude critics. This is a good article.
And I like to add two more very very commonly very very frequently used polite words: Please , excuse me, thank you. always use these key words to start or end every of your conversation.