What is method to found valency and oxidation state.
First get thorough with the position of elements so that u can know the valency but u have to study the oxidation statea
if u know how to find oxidation number it will no necessary to know valancy
To find valency,
We have to calculate electrons in outermost orbit of that electron.
And for O.N.,
O has O.N. 2,
H has O.N. 1.
from these O.N. of others can be calculated!