Etiquette problem?

I have always thought that I have fairly good understanding of etiquette, and how to behave in different situations, what to do, which fork to use and so on. Big thanks to my parents being so strict on manners when I was a child.
But I have now received an invite to Japanese Tea Ceremony for Saturday! Not for a tourist place, but to my colleague's family home, for ceremony hosted by his mother. 
And my mind is blank! I have heard all the stories of the strictness of the traditions and rituals, but never been in one before and it is not something that you get exposed as westerner that often.


I have had a look of this website: Japanese Tea Ceremony , but I think I got even more confused when reading it!
If you reading this, and been in one before as guest, please do send me your tips!

Picture from the same website: Japanese-tea-ceremony.net. My current guide!

I will post story and pictures afterwards. Keeping fingers crossed that everything goes well and that I don't embarrass myself or my hostess!