The vessel
A green tea setup begins with the vessel, and the one to choose is a porcelain gaiwan（盖碗）of 100 ml.
It is wide, shallow and thin walled, and all three of those help a leaf brewed below boiling.
Wide means the liquor cools as it pours, which stops the leaf cooking in the last few seconds.
Shallow means you can see the leaf and lift it out the moment it has given what you want.
Thin walls mean the vessel takes heat from the water once at the start rather than holding it.
A glass cup of 250 ml is the alternative, and it is the better choice for a bud grade.
Glass shows the leaf opening, and with a green bud tea that is most of the reason to brew it.
A small porcelain pot works too, though it gives you less control over when an infusion ends.
Whatever you choose, it needs a lid that fits and a rim that pours without dribbling.
A lid that rocks lets heat out, and a rim that dribbles costs you seconds you do not have.
Both faults turn a short infusion into a long one, and a long one is what spoils green tea.
Pick one vessel in one size and use it for everything, because consistency teaches faster than variety.
Water and dose
Water temperature is the first setting, and green tea wants 80 to 85 °C rather than boiling.
Boiling water on a bud grade produces a flat, stewed cup within the first 30 seconds.
A kettle with a temperature dial does this automatically, and a probe thermometer does it for less money.
Pouring from a boiled kettle into a cold cup drops the temperature by about 5 °C, which is worth knowing.
Dose is the second setting, and 5 grams in 100 ml is the standard ratio.
That looks like a lot of leaf, and it is, because the infusions are short.
Weigh it on a scale reading to 0.1 g rather than spooning it, since leaf density varies wildly.
A tightly rolled leaf weighs far more per spoon than a flat one, and the difference is a whole grade.
Water quality is the third setting, and hard water flattens a delicate tea more than people expect.
Filtered tap water is fine in most places, and distilled water makes a thin, hollow cup.
Use water with some mineral in it and no chlorine smell, and the rest takes care of itself.
Temperature, dose and water, in that order of effect on the cup.
Scale to taste
Once the setup is fixed, the only thing left to adjust is time, and you adjust it by tasting.
Hold the first infusion to 30 seconds, pour it out completely, and drink it before doing anything else.
A thin cup wants about 10 more seconds on the next infusion rather than more leaf.
If it is bitter or drying, take 10 seconds off, and check the water is not too hot.
Bitterness from heat and bitterness from time taste different, and learning the difference is the whole skill.
Heat bitterness arrives at once and coats the mouth, and time bitterness builds slowly at the back.
Run a session to three or four infusions, extending each one slightly as the leaf gives out.
A green tea usually peaks at the second or third infusion and falls away after that.
If it peaks at the fifth instead, the water was too cool or the dose too small.
Write the numbers down for the first few sessions, since memory for these things is poor.
After a week you will be adjusting without measuring, and the setup becomes invisible.
That is the point of a fixed setup: it removes every variable except the taste.
Common mistake
The most common mistake in a green tea setup is using water straight off the boil.
It is also the easiest to fix, and it is the one that ruins the most good leaf.
The second mistake is a vessel too large for the dose.
Three grams in a large mug is a weak tea no matter how long you leave it.
The third is leaving the leaf sitting in water between infusions, which undoes the short steep entirely.
Pour every infusion out completely, and never let the leaf sit in the last of the liquor.
The fourth is buying a set rather than a vessel, and ending up with a tray you never use.
The fifth is chasing the vessel instead of the leaf, which is where most of the money goes.
A good tea in a plain gaiwan beats a poor one in anything, every single time.
The sixth is measuring by eye, which drifts by a gram or more between sessions.
A gram changes the cup, and a scale costs less than a sample bag of the tea.
Fix the temperature, weigh the leaf, pour completely, and the category stops being difficult.