Legal Question in Real Estate Law in California

Voluntarily? Or against their desires? The former is done with a deed, properly filled out, signed before a notary, delivered to the new owner, and recorded.

If you need to remove someone that is unwilling to give or sell you their portion of ownership, you sue them to "quiet title," and you'll need sufficient grounds and some time and money.

If they consent, they give you a deed to their interest. But you don't file a quiet title against a coowner who legitimately has title. If you can't agree on a buyout, you file a complaint for partition by sale.

Both the previous answers are mostly correct. If the person is willing to give up title, a deed is the method. If they are not, it depends on why you think you have a right to have them off title. If they are wrongfully on title, a quiet title action is the method. If you are just joint owners and don't want to be joint owners with them anymore, then the partition action is the method.