Disclaimer: This is only general information, it is not legal advice.
Legal: Putting your affairs in order:
Majority of people pass without having a will, advance health directive, estate plan and other needed documents. This section lists and outlines California-specific legal paperwork that simplifies the process.
California Advance Health Care Directive
The Advance Health Care Directive can be used to appoint a family member or friend to make health care decisions for you if you are physically or mentally unable to make those decisions yourself and to appoint a specific family member, friend, etc to take care of your funeral arrangements. Similar documents are also called Durable Powers of Attorney for Health Care. One specific part that pertains to funeral arrangement is described in this clause:
"(1.5) AGENT’S POST DEATH AUTHORITY: My agent is authorized to make anatomical gifts, authorize an autopsy, and direct disposition of my remains, except as I state here or in Part 3 of this form..."
Please note that most of the time when you fill out Power of Attorney form at a hospital, it is only financial or medical decision making related and ends when person passes.
More information can be found at California Department of Justice Office of Attorney General website and the form is found here. It requires two (2) witnesses and possibly a patient advocate or ombudsman.
Will and testament, trust and naming of children's guardian
Writing a will can be as simple as typing out how you want your assets to be transferred to loved ones or charitable organizations after your death. If you don't have a will when you die, your estate will be handled in probate, and your property could be distributed differently than what you would like.
It is best to contact a will/trust specializing lawyer if you own property or other high value assets.