When my Mom used to make tea, she would always rinse the pot out with boiling water before putting the tea leaves in, and she always measured out a rounded teaspoon of tea for each person plus "one for the pot."  Is there any reason for either of these rules?

--Janice

First off, I'll bet your Mom was drinking black tea, which includes the most popular Orange Pekoe kind.  Black tea needs to be brewed at close to the boiling point for water.  Most sources recommend using water somewhere around 203°F (95°C) or warmer.  A porcelain or ceramic pot absorbs enough heat from the water to cool it down substantially. Black tea is usually allowed to steep between 3 and 6 minutes.

In a quick test in my own kitchen, I boiled water at 208°F (98°C).  I live nearly 2000 feet (610 meters) above sea level, so the boiling point of water is lower (see High Altitude Cooking).  When I poured boiling water into my ceramic tea pot without preheating it, the water temperature fell immediately to 195°F (91°C), well below the recommended brewing temperature for black tea.  When I repeated the same experiment but first rinsed the pot with boiling water and then filled it, it was a perfect 203°F.

Different types of tea need to be brewed at different temperatures and for lengths of time. Green and white teas are brewed at around 170°F - 185°F (77°C - 85°C) and steeped for about half the time as black tea.  Oolong tea is brewed closer to boiling temperature, but not quite as hot as black tea and steeped up to about 5 minutes.

All of that said, the rules for temperature, as well as amount of tea leaves, and pretty much every other tenet of what makes good tea varies from region to region and author to author.  McGee goes as low as 110°F (43°C) for brewing green tea.

As for the habit of adding "one for the pot," I almost suspect that to be a marketing ploy by the tea companies to make you use more tea leaves.  The only plausible reason I can come up with is that perhaps the "one for the pot" rule makes up for the fact that a smaller amount of water will cool faster because it will have a greater surface to volume ratio.  Using more tea would compensate somewhat for the lower extraction rate you would get at an on average lower temperature.  If that is the case, then reducing heat loss from the pot would make more sense than using more tea leaves.  The standard way to do that is with a Tea Cosy.

Other 'rules' for tea include always using fresh cold water, because it contains more oxygen which improves the flavor, and not using hard water, that is water with a high mineral content.  Minerals can cause the tannins in tea to precipitate out and form solids that float in the tea or form a scum on top.  Although I always use fresh cold water, I am not sure how much of a difference it actually makes.  It might be worth a blind taste test some day to see if I can really tell the difference.

Tastes in tea, however, are very subjective.  Some people prefer their tea to be darker and have a more bitter flavor than do others.  When I first met my wife, we would go to her parents on occasion.  Ruth and Norm drink their tea a lot stronger than what my Dad used to drink and therefore what I grew up with.  The standing joke at my future in-laws' house was, "Dave, we're about to pour the water into the tea pot, so you better get your cup ready."  A jab at the fact that I like my tea weaker and therefore didn't allow it to steep nearly as long as they did.