If you can, please tell what i'm missing or what's wrong. I want to try it and complete simple, yet effective guide
This is what i wrote from my own experience and tips that i received from other people.
Even the best green tea will have bad taste when prepared incorrectly. Few simple tips will help you to enjoy japanese green tea. This is not necessary absolute truth that you have to follow all the time.
1. Most important component is water. For brewing use only filtered or bottled water without mineral supplements.
2. Temperature of water also affects the taste greatly. Boiling water makes tea more bitter and creates strong astringent taste.
Recommended temperature:
Sencha - 80-85C
Sencha high grade - 60-75C
Gyokuro - 60-70C
Gyokuro high grade - 40-60C
Genmaicha - 80-99C
It's possible to lower temperature for more mild and soft taste or increase for more stronger and rich taste.
To get lower temperature without thermometer you can use simple technique. Before making tea pour boiling water into teapot(kyusu), wait until teapot will be hot, pour water from teapot to your cup, put tea inside teapot and use water from cup to brew tea. This technique will allow you to get water with temperature about 80C and also will pre-warm your teapot and cup, which is also good thing to do.
If you want to drink green tea often I would recommend to purchase electrical thermos with temperature control. It will spare a lot of time because what you will have to do is only press button and pour enough water into teapot.
A lot more cheaper way is to get cooking thermometer which will help a lot to maintain green tea taste from cup to cup.
3. Don't make tea in cup. Green tea needs quite a lot of space for brewing, it is strongly recommended to use teapot(kyusu).
4. Never leave water in teapot, remove all water or on next infusion will be really bitter and will have strong astringent taste. Also it is not recommended to add hot water to your tea if it's too strong, better change temperature of water/amount of tea used/time of infusion.
5.Usually one teaspoon of green tea is used for about 200ml. Time of tea infusion is usually around 1-2min. For sencha and genmaicha with temperature of water higher than 80C 1min. is enough. You can infuse green tea 3-4 times, but don't use leaves that were left overnight. For next infusion add about 10-20sec., but this is a matter of taste. If after infusion of genmaicha or certain types of sencha has been more than 5min on next infusion pour tea to your cup immediately.