which ATC frequency would you call?
On the Sectional chart for SFO there are these little boxes with "CTC NORCAL APP WITHIN 20NM on 1xx.x 3xx.x". So what you do is find out where you are, look on the chart for the nearest box and call them up on that frequency with a call something like:
"Norcal approach, NXXXXX request"
they'll come back with something like
"NXXXXX go ahead"
then you reply with something like
"NXXXXX is a P28A slant A [equipment code of a/c] 5 miles south of Halfmoon bay, 3500 request VFR flight following to Long Beach"
They'll issue a sqwark and once you hear the reply something like "NXXXXX radar contact, 5 miles to the south of Half Moon Bay" you are being flight followed. Once you near the limits of the controllers airspace you'll be told to "NXXXXX contact Norcal approach on 1XXX.X".
You call to the next station would be along the lines of "Norcal approach, NXXXXXX with you 3500 (request climb to 11500)" or something.
You can get the initial frequency from the Jeppesen airport guides (or the FAA Airports Facility Directory) which have the approach facility / frequency printed on them, so in my above example under HAF you'll see that its got listed :
(R) Bay App / Dep Con 135.1 (my books out of date, its been replaced by NORCAL). These are the people you'd call for VFR flight following.
When under flight following, its best to 'request' altitude changes rather than just do it, unless they say "report changing altitude". Often they squeeze in IFR traffic around you and you might give them a shock if you just change level. They may also come along and tell you "VFR descent approved" even though you didn't request it. This is becasue they know your flight profile to some extent, and know you will want to decend soon. Its up to you if you descend or not, so long as there is no overlying class B airspace.
In my little scenario, Norcal would hand you off to Norcal, who would hand you off eventually to LA centre who would probably hand you off to Santa Barbara approach, who would hand you off to Point Magu USMC station who would hand you off to Socal Approach who would hand you off to Long Beach Tower. Remember that if receiving VFR FF you are cleared through any Class C airspace en-route (the Magenta surrounding medium sized airports,like Santa Barbara).
Cheers
EA