Getting around 35 mpg at best?

All you can do is avoid the things that consume the most gas.

Use the traction motor (electric only) to get going from a stop. That's where most ICE cars waste gas...breaking inertia. Avoid complete stops where it's safe (you're forced to break inertia to get going again...slowing to 2-3 MPH is enough). I like to electric-only to 15 mph if I can, but it's important to not floor the pedal in a way that makes the ICE kick in from a dead stop.

Accelerate HARD to get to a desired speed and then let up. Experience shows for most hybrid owners that you waste more gas using the ICE to get to a desired speed slowly than a hard acceleration. It's the difference of less fuel for a longer time or more fuel for a shorter time. It appears the hard acceleration uses not that much more fuel, so it's a gas saver in the long run.

Allow more time to get where you are going or don't be in a rush to get somewhere. If you have plenty of time and aren't holding up traffic, you can coast along at below the speed limit and save gas or run only on electric rather than use gas to go faster.

Set your cabin temp for what is comfortable year-round. Too hot/too cold will tax the system more and cost you energy. I like 72 F.

Set your tire pressure right. I've been using 42 PSI on all tires with good results. Underinflation = wasted gas. Slight over-inflation (at worst) = harder ride.

Pick routes that avoid going uphill. Load on drive system = using gas. I take a slightly different route into down because it avoids a big hill I'd have to use the ICE to climb...even though I get to coast down the other side. The other route can be done entirely without the ICE kicking in.

TAKE YOUR PRIUS OUT ON THE HIGHWAY (or back country roads) every now and then to see what MPG you get when you drive 45-55 unimpeded by traffic and stops. It'll let you know if you really have a MPG issue or not.

 

In the Bay area with lots of hills and driving style is giving you the mileage you're getting. Can't do anything about the hills, but you can influence mileage to a great degree with your driving style. Hate to see what your mileage was on your previous vehicle, and I'll bet the Prius even at 35 mpg is much better!

 

Reset the mileage meter, it's possible you're running on the average including the dealer prepping your car, actually, unhook the 12v battery and start fresh.
42-40psi in the tires, cycle the emergency brake a few times to make sure it's not dragging, briskly accelerate to speed and don't go over the speed limit.
Living in a flat area is going to reduce your mpg's a hilly area has lot's of gravity involved, gravity and inertia=prius proving ground
Check the level of the motor oil, if it's to full it could be problematic. If you're not spending hours on a freeway at 75mph you're 20mpg's low.