In no particular order:
Milk before or after?
Originally all the cups in Europe were made from soft paste porcelain. The milk was added first to temper the cups from cracking. Once hard paste porcelain was discovered in Europe (Bottger in 1710) it was no longer necessary to temper the cups. Hence it makes sense to add milk after the tea has been poured into the cup according to the strength of the brew.
Lower class people, who could not afford porcelain cups, poured milk in first to protect their cups that might crack as a result of the boiling tea.
However, tea emulsifies the fat in milk leading to a creamier flavour, so it is a matter of taste.
Holding the cup: Hold the cup with the thumb and fingers. Do not curl a finger through the handle. While once fashionable, the pinky finger should not be extended.
Drinking the tea:
If at the table lift the cup from the saucer and drink. Do not lift the saucer.
If standing, lift the cup with the dominant hand while holding the saucer with the other.
Look into the tea cup when drinking, never over it.
Never swirl the tea in the cup. It would be embarrassing if some should slosh onto the table cloth.
Stir the tea gently back and forth from the six to 12 o'clock position to avoid clanking the sides of the cup.
When not in use, place the teaspoon behind the cup to the right of the handle.
A tea superstition (likely French): To put milk in your tea before sugar is to cross the path of love, perhaps never to marry."
Extra information: In A Social History of Tea by Jane Pettigrew in the 18th century, it was customary for highborn ladies to receive callers with their morning tea while "abed and bare breasted."
