I was in SF about two weeks ago and when I visited the Train Museum (probably a different official name), the agent gave me some pointers:
(1) A bus (trolley) transfer is good until the cutoff time, generally two to four hours (depending on how nice the driver is) on any buses or muni trains in that period of time, this includes multiple trips as well as a return trip to your starting point.
(2) Seniors (over 65) pay only $0.50.
(3) They are using reconditioned trolleys (which get as far as Fisherman's Wharf), which were originally used in places like Italy, Germany etc. For nostalgic and historic reasons these are fun to ride.