Travelling north on Highway1/101, cross the Golden Gate Bridge. Once you get across the bridge, there will be an exit for Golden Gate National Recreation Area. Follow the park roads to various overlook points for the Golden Gate Bridge and Point Bonita lighthouse.
I visited Golden Gate N.R.A. in early April, and it was very wet. Rain gear is a must. You will also want a tripod as the best shots of the lighthouse are at dusk...the best shots of the bridge are at night when it is all lit up.