Open jawed and free stopovers
Hi Jason,
You have a lot of flight options which I'll briefly explain.
1) Flying into one airport and out of another is called an open jawed flight. The cost is (in the example you use) half of the return airfare to LA plus half of the return airfare to San Francisco.
2) When you buy a return transatlantic ticket you qualify for a free stop over. Thus you could fly to Las Vegas, see Las Vegas and surrounds. Fly to LA. Fly home from San Francisco for the same price as 1) above. Las Vegas is the free stopover in this example, but it could equally be Denver or New York.
3) The thing to watch out for when doing an open jawed flight are drop off charges for picking up a car in one place and dropping off in another. However, you may well get away with picking up in LA and dropping off in San Francisco without drop off charges.
I hope that this helps.
There is an lot more on
http://www.uk-2-usa.com