The accuracy of parcel boundaries varies considerably, with errors ranging from just a few feet to 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.