These are required for every transaction and contain a wealth of information that may or may not apply to the type of home you are searching for. It's all general information.
Taking a moment to review these during your search before you find a specific property of interest will ensure they aren't rushed through or looked past. Links to all documents are at the end of this post.
Your guide to the Home Energy Rating System is provided by the California energy commission. It contains information about energy ratings, energy efficiency, and laws related to energy efficiency in California.
The Homeowner's Guide to Earthquake Safety is published by the California Seismic Safety Commission and contains information about the different types of earthquakes and the various kinds of damage they may cause to structures.
Protect Your Family from Lead in Your Home is one of the many documents/pamphlets/booklets that deal with lead paint and the hazards it can present to you. Lead-based paint has been illegal since 1978, but many homes in SF have covered layers of paint that may contain lead.
The Residential Environmental Hazards document contains a wealth of information about hazards that may exist in homes, or hazardous conditions that may be created by natural disasters or other events. In general, you can think of this document as the "(almost) everything that can go wrong" document.
Links to General Info Booklets
PDF format, adobe acrobat reader required.