First, get good tea. Supermarket teas are right out, as are tea bags. Tea bags from supermarkets are doubleplus ungood. A basic chun mee or an average sencha should set you back five to eight euros for a hundred grams, and that's on the expensive side.

Second, get a proper teapot. That's simple enough. Get a strainer, too, so you don't get too many leaves in your cup. You'll obviously need a teacup or several too.

Third, you should have ready access to freshly boiled water that doesn't have too extreme Ph values. The plain old tap water around here is very regular and quite good, so I can't give you any advice there. Get a stopwatch too; I picked my cell phone specifically for the stopwatch feature.

Now that the materials and tools are on hand, boil cold water. Then pour about a cup (1,5 decilitres) of cold water per litre of hot water in, to lower the total temperature. Warm the teapot with hot water at this point if you want to; I rarely bother anymore. Measure a couple of grams of loose tea into the slightly moist teapot. Depending on how dense the tea is, a gram might not look like anything. Knowing much should be used of which particular tea comes only with experience, so don't be afraid of messing up (though it might be better to mess up by using too little leaf rather than the other way).

Then pour hot water on the leaves, start the stopwatch and close the teapot. Observe the stopwatch for fifty seconds to a minute, and then pour all of the tea out of the teapot through the strainer, into cups.

Drink. Steep again if you want to. Greens can be steeped anywhere from two to five times, depending.

Other kinds of tea require different parameters to come out well, but the three main ones (besides the quality of the tea itself) are temperature, quantity and time.