A violation of Div. I 7.2.35 , aka Parking on Grades, aka Block Wheels, aka Curbing your Wheels will cost you $50. But tickets for this violation are often given out erroneously because unfortunately, some DPT officers don't know that in order to cite somebody for violating this traffic code, the street must be a grade of 3% or more.  A 3% grade is actually 1.72 degrees (picture a 45 degree ramp). It looks almost flat.  Many of these citations are written in error because DPT officers can't possibly know the specific grade of every street in SF. And many of these erroneous tickets are paid erroneously by us, because how could one possibly disprove it?
Here's how young grasshoppa':
Go to The Surveyed Streets of San Francisco by clicking here. On the list of resources click on The Surveyed Streets of San Francisco. Once there, enter a street name, and then set the limits (cross streets). Being a government site, it doesn't won't function properly the first time and won't let you enter the cross street. So click search. It will give you an error message but it's okay. In government systems, that means that it is working now. It now will allow you to choose the cross street limits. Scroll down to the nearest cross street where you were parked. Once the map comes up, click on "grade" on the right side and the percent grade of your block will be in the center of the street. 
If it's less than 3%, then your ticket was written in error. Contest the ticket, include a printout of the evidence, and you are home free.
This will literally take you 2 minutes to verify, 1 minute to contest, and 45¢ for a stamp. But, unless you have surveying tools in your trunk, do yourself a favor and save $55 by making it a habit to curb your wheels.

Another slam dunk way to get out of a bogus ticket is using the 100 foot rule. 

The SF traffic code states:
The City Traffic Engineer shall erect and maintain signs noticing any Parking restrictions not more than 200 feet apart. The signs shall indicate by legible letters, words and figures the hours prescribed for said Parking restrictions within 100 feet on either side of the sign...
In English, this means that each sign is enforceable for only 100 feet.  If you received a ticket and you believe that the sign was more than 100 feet away, it's easy to contest. Measure it. Get a tape measure and measure the distance between the signpost and where your car was parked. If it was more than 100 feet away, and you contest it, your ticket will be dismissed. SFMTA will measure it also, and then send you an apology.  By the way, there are many spots all over the City that have gaps of over 100 feet between any restrictive sign. They have been hidden in plain sight for years. This means that you can park there for free for 3 days... actually 4 to 6 days minimum depending on your relationship with your neighbors, but that's a story for another day.
To learn where these golden parking spots are, or for any other parking related question, click here.