Of course, if you are much lighter or heavier than average your most frequently used sail will differ. A full quiver will generally include sizes as small as 3.5 and as big as 6.0. Many shops offer lessons for first time beginners up to advanced sailors. Information on how to contact them is listed on the SFBA Shops page. Great places to learn include Shoreline Park, Foster City Lagoon, the Delta and Lake del Valle.
Most shops have equipment for rent or demo.
Note that many shops do not rent wetsuits. Information on how to contact them is listed on the SFBA Shops page. The SFBA Links page has a large list of sites. Among the best are Call of the Wind and Windsight . Additionally, there are some public windtalkers that are useful.