As naive as this may sound, when I first moved to America and was deciding where to base myself, I first had to learn that there was a difference between Silicon Valley (i.e. Peninsula / South Bay) and San Francisco.

From there, San Francisco looks quite small, but many neighborhoods are worlds away from the action - Outer Richmond is not the density of networks you are looking for, for example (better than rest of world, suboptimal for SF).

Co-locating close to the center of these dense founder networks is the best way maximize luck and opportunity.

This map isn't perfect, but it makes it pretty obvious where you should move if you're interested in startups.

Career wise, moving to "the center of the network" is still the best decision I ever made.