I’ve done it and posted here about the process. The potential savings are huge, and I am amazed more people don’t take advantage of their rights to appeal.
The process is relatively simple and easily understood if you just work within the rules provided by the county Assessor’s office. The trick is to get your fair market value as of January 1 of this year. So only go by comparable sales prices on that date plus or minus 3 months. Nothing else, including today’s value, is relevant. Use your realtor sources for that, or internet research tools.
Right now, the appeals docket is overwhelmed with thousands of appeals–over 14,000 as of a few months ago. I see that number doubling or tripling as values fall further and people wake up to the possible savings. County officials may be so unable to process all these appeals that they simply grant you your requested number.
They have two years from the date you submit. One of my appeals is from last November and they haven’t even responded (but I know I am in their records–they give you a number).
The sidebar to this story is that county and city governments will see property tax revenues drop. The happy and fat years of 10% plus revenue growth and corresponding government bloat are over. Look for the new veto-proof CA legislature to end your Proposition 13 protections after the election.