We drived by car from San Francisco.
The best way is:
From SFO take freeway 80 west, next 580 west,205 west and finally 120 road west. You will arive in BIG OAK Flat Enterence /Yosemite Natl Park/
If U want to see Gaint Sequoias You have go to Mariposa Grove which is located close to South Enterence of Park.