Water Quality
When brewing tea, it is very important to first ensure that you have a source of good, clean water.  Light-steamed Japanese tea is especially sensitive to water quality, and so any water impurities will noticeably alter the final flavor. We always recommend bringing the water to a full boil and then allowing it to cool down to the desired temperature before brewing any of our teas. Boiling the water for around 3 minutes can significantly reduce the flavor of chemicals like chlorine.  Be careful not to boil the water for too long, though, or it will become flat and flavorless.  If possible, use soft water (with a low mineral content) to allow the leaves to infuse more fully. Remember, good water can make all the difference when it comes to brewing a good cup of tea!
Water Temperature
Next, it is critical to take note of the temperature of the water.  Japanese green teas can easily become bitter very quickly if they are steeped in water that is too hot.  If you do not wish to wait for your water to cool after boiling, you can pour some into a small pitcher, called a yuzamashi in Japanese, or into the serving cups.  Pouring the boiled water into cups to cool is a great way to ensure that you use the appropriate amount of water while also warming the cups enough that the tea will not cool too quickly after serving!
Finally, keep in mind that the following guides are recommendations, not rules. Start with these steps and work from there to find a brewing method that best fits your taste. Lowering the temperature will reduce bitterness, for example, but might also require a longer brewing time to reach the strength you desire. Using a higher ratio of leaf to water will mean that you can make many more infusions, but should also significantly reduce the brewing time. Each tea has the potential to produce a variety of flavors and aromas, so take your time to experiment and discover all of the possibilities!