SFO Airport is easily accessibly via subway (BART) , taxi, or shuttle, but the best transportation options usually depend on the day and time of day that you are traveling.
Shuttle to SFO
If you’re not pressed for time, riding Super Shuttle is usually the fastest and cheapest way to to get to SFO airport. The price is $17 dollars fixed, though if you are feeling nice, you can tip the shuttle driver a dollar or two.
Super Shuttle will also pick you up at your house, and drop you off at your appropriate gate.
The primary complaint with riding Super Shuttle is that sometimes they will take 30-45 minutes picking up other passengers before taking you to the airport. Alternatively, sometimes you will get lucky and be the last person picked up, so you they will drive directly to SFO airport after picking you up.
BART to SFO
Outside of getting a ride to the airport from one of your friends, BART is by far the cheapest way to get to SFO, but can still cost about $7 from most BART stations in the city.
BART can also be the slowest way to get to the airport, as they do not always run frequently, and they can sometimes experience delays.
If you are trying to get to the airport around rush hour, BART can be faster than super shuttle or even a taxi if there is lots of traffic on Highway 101 (which there usually is)
Taxi to SFO
Taxi rides are the fastest way to get to SFO, but they are also the most expensive. Taxi ride prices are not fixed as is the case in some other cities, and usually cost about $40. If your driver drives slowly or encounters traffic, the taxi ride can cost $50-60.
When getting to the airport late at night or early in the morning, and if you are traveling in a group of two or more, Taxis are usually your best option for getting to the airport.