Transfer from San Francisco Airport

[maz]

Hi,
I'm off to San Francisco in 2 weeks time staying there for 3 days then going to New Zealand, Australia, Singapore. Frisco is the only place transport not arranged so would be grateful for any advice on the best way into the city, near Fishermans Wharf, bearing in mind my sister and I are in our sixties. Would appriciate any help given.
Kindest regards
Maz