What is proper etiquette of lunching at a tea room?

I want to take my girlfriend out for a girl-day on her birthday , and lunch at a beautiful tea room I’ve been eyeing for a long time. I’ve been to a tea room once before, but as a guest of a large party. This would just be the two of us.

What is the appropriate etiquette? Is tipping expected, and how is it done? is there a certain code of dress? Any information would be wonderful.

Thanks!