Signature and date of birth: Run your finger over the signature: you can FEEL it! And the date of birth is in raised letters over your photo.
Hidden photo: In addition to the full-sized and small photo, there is a third "hidden" photo hologram that is only visible under backlight. On older cards, you'll see a hologram of a walking bear.
CA brown bear: Hold your card in front of a light; you'll see a brown bear magically appear on the right side of the card, outlined by pinpoints of light.
Micro text: I didn't see this mentioned in the DMV flyer, but it's there. Take a look at the word CALIFORNIA, and use a strong magnifier to look at the line under it. In tiny letters, you will see a line of words written immediately under that line. I'll leave it to you to find out what it says.
I have a little Digimark backlight/magnifier that I carry with me. It's inexpensive and a good tool to fight fraud. You can find this or a similar tool wherever you get your Notary supplies or through an internet search. I use it at every notarization, and make a quick journal notation to verify the presence of the hologram and micro text.
The DMV has issued a flyer discussing changes it has implemented:
http://www.dmv.ca.gov/pubs/brochures/dl/dl627e.pdf
Be safe, don't notarize for a con artist.
CHECK THE IDs!