We meet upstairs in Red Rock Coffee. I usually get there early and occupy a table. Red Rock appreciates it if most of us buy something to drink/eat.
I try to provide some talking points a week or so before each meeting. Generally, we focus on the "Live Better" part of the Sunday Assembly's purpose. There are no prerequisites.
I sometimes post summaries of our discussion in the comment sections of past meetings, which can be found through meetup.com/Sunday-Assembly-Silicon-Valley/events/past/ (I don't know a better way).