With more and more airlines announcing flights from Australia to San Francisco (Qantas just announced flights from Brisbane and Sydney) you may find your self passing through San Francisco Airport (SFO) at the beginning or end of your journey. We recently flew from Sydney to San Francisco at the start of our around the world trip and found the airport to be very easy to navigate, with plenty of spots to sit and relax before your next flight.
We had an early morning flight so luckily the airport was not very busy when we arrived, and check-in and bag drop were even easier with clearly marked signs for the cabin classes and airlines (this may differ depending on your airline).
Moving through security was a bit slow, so it is a good idea to prepare yourself while you are waiting, getting your laptop or tablet out of your bag, making sure your pockets are empty and you have proof of ID and your boarding pass ready to go. You will also have to remove your shoes and dispose of any liquids that are bigger than 100mL. Once you are through security there is space for you to organise your bag again including seats to put your shoes back on.
We were flying out of Terminal 3 with United but there are a total of 3 domestic terminals with Southwest and Delta in Terminal 1 and American Airlines in Terminal 2. In Terminal 3 when you exit security there is a map of the terminal right in front of you, with gates and shops towards the right as well as more gates straight in front of you. There is also United lounges in both directions. Depending on the location of your gate you will find similar shopping and dining options, including a range of restaurants, convenience shops and luxury shopping.
Transferring between terminals at SFO is easy on the AirTrain, there are two lines and both visit all of the terminals. If you need to transfer from terminal 3 to international terminal G this can be done at the left end of the terminal, the same can be done between terminal 1 and international terminal A. It is also possible to walk through to the other terminals without going back through security.