I use a small gaiwan (10cl) to brew chinese green teas, and sometimes
oolong teas.
When I try a green tea for the first time, I use about 2 grams of leafs
(I don't weigh it) and water at 80°c (= 176° fahrenheit). The first
infusion lasts only 10 seconds ! The following infusions are longer and
longer (eg 10s 15s 25s 45s 1'15 2' 3'30 5' ...)
Then, I try to adjust the brewing time according to my taste, playing
only with the brewing time. I think changing only one parameter at the
same time is a good idea.
This is my way of doing, which corresponds to my personal taste. Yours
will certainly be different, but this is just a proposition of starting
point.

Brewing green teas in a gaiwan makes heavenly infusions, to my taste.
Though, I never tried to brew green tea in a Yixing teapot. I am
interested in the experiences of the followers of this method : do you
need a specific kind of Yixing teapot (shape, thickness,...) ? How many
grams of leafs do you use ? What is the temperature of your water ? How
long last the infusions ? ...

Valéry