When I am ready to sell my car, can I just sign the back of the title and give it to the buyer?

Yes, you can, but there are many reasons why you shouldn’t. The most important reason is that you will have no written record of the sale. Also, you have to sign in front of two witnesses other than the buyer, and one of them has to go with the buyer to the Notary Public to swear that he saw you sign as the seller. Should any error be made during that transaction, your signature will be needed anyway to correct the mistake.