1) Balance nitrogens by adding coefficients.
2) Balance oxygens by adding water molecules.
3) Balance hydrogens by adding protons.
4) Balance charges by adding electrons.
2NH2OH ---> N2O + H2O
2NH2OH ---> N2O + H2O + 4H+
2NH2OH ---> N2O + H2O + 4H+ + 4e-