A deed must always be notarized and filed in the public records; it may also have to be witnessed.
The person who will sign the deed (the person who is transferring the property) should take the deed to a notary public, who will watch the person sign the deed and will sign and stamp it. The notarization means that a notary public has verified that the signature on the deed is genuine.
In some states, deeds must also be signed by witnesses who watch the owner sign the deed.
The person who signed the deed should "record" (file) the deed, with its notarized signature, in the land records office in the county where the property is located. This office goes by different names in different states; it's usually called the County Recorder's Office, Land Registry Office, or Register of Deeds. In most counties, you'll find it in the courthouse.
Recording a deed is simple: Just take the signed, original deed to the land records office. The clerk will take the deed, stamp it with the date and some numbers, make a copy, and give the original back to you. The numbers are usually book and page numbers, which show where the deed will be found in the county's filing system. There will be a small fee, probably no more than $15 a page, for recording.
For step-by-step instructions on creating and filing a deed in California, see Deeds for California Real Estate, by Mary Randolph (Nolo).