[akahn]

A good trick is to listen to the water boiling. At around 180°F the water starts bubbling and dancing, gets a bit agitated and might make a resonant sound in your kettle. I suggest using a thermometer and getting to know how the water sounds at different temperatures.

Best place to buy tea: http://uptontea.com/ Top notch quality, and they put out a really good paper catalog describing all their hundreds of teas quarterly.

[silentbicycle]

When I boil water in an open pot, I can usually recognize the different temperatures by the way the water shimmers, the size of the bubbles, etc. Do that a couple times with a thermometer, and you can probably eyeball it from there.

I've heard the stages of boiling referred to as "dragon eyes", "fish eyes", etc. See e.g. http://www.veetea.com/site/articles/Water-Temperatures/ .

That said, my wife and I got an electric teakettle with a temperature setting as a wedding gift, and we love it. That's another option. (This one, or a similar model: http://www.amazon.com/Choice-SmartKettle-Cordless-4-Quart-El... )

[eru]

I heard that you should boil the water first, and then let it cool down. The listening method only works when you don't boil it, but go to the desired temperature without a detour.

[KingOfB]

Another vote for Upton Tea. Great place.