All Downton Abbey fans are going to be glued to the television for the final season and with it we will all be making endless cups of tea (to get into the spirit of things) along with a few Downton Abbey parties to give them a final send off. To help you to know the ins and outs of tea making, download Afternoon Tea Downton Abbey Style by Tadio Diller.
Note: It was free for Kindle when I downloaded it and is quite a short book, but does let you know the difference of types of tea and how long to brew along with recipes.
More info. about afternoon tea and customs here
I found an interesting article on tea etiquette at Huffington Post
High Tea or Low Tea?
There is some confusion over high tea and low tea. High tea is served on a dinner table usually between 6 and 7 p.m. Low tea or afternoon tea, is served around 3:00 - 4:00 p.m. on a lower table (coffee table height) in a living room/drawing room.
Note: napkins are never put on the table once they have been on your lap (folded at a diagonal). If you need to leave your chair, your napkin should be placed on your chair until you return.
Lots of info. about tea etiquette here