This kind of question is exactly why we provide our services here. There are so many companies to choose from that people usually feel overwhelmed.
I would recommend creating a profile our our website, and searching through solar reviews on our San Fransisco page. Read over reviews for several installers, and click the "plus" button next to them to add the installers to your profile. You'll be able to compare multiple installers from your profile, giving you a better idea of what to look for.
Then, read over our "Comparing Companies" section to learn more about how to narrow down your list further.