Since you have an indepedent voltage source and current source; start with the following:
1) Deactivate the independent voltage source by shorting it, and calculate the nodal votlages and currents.
2) Deactivate the independent current source by opening it, and calculate the nodal voltages and currents.
I honestly do not remember the "format" approach. You should have a set of equations that you can combine together and solve for Vo.