The accuracy of parcel boundaries varies considerably, with errors ranging from 10s, and even 150 feet in some areas. Parcel boundaries were adapted from Assessor Department CAD drawings, and then rubber sheeted to form a seamless layer for the whole county. There is no substitute for using a licensed surveyor to locate your property corners. Should you be lucky enough to locate a monumented property corner, you could use the metes-and-bounds on the Assessor's Parcel Map (see question Number 1) to approximate the boundaries and remaining corners.
Please don't attempt to use the My Neighborhood Latitude/Longitude tool and a GPS device to locate a property corner, as both of these tools will introduce significant error.