In light of stories like this:
we need to take precautions so that if we're ever wheeled into the ER unconscious and hooked up to a ventilator, we won't be euthanized and carved up for our organs.
i) Assiduously cultivate an unhealthy lifestyle. Be obese. Look like Dan and Roseanne Conner from the sitcom (Roseanne).
ii) Carry one or two packs of cigarettes on your person (in a purse or shirt pockets). You don't have to smoke them. They are just stage props.
iii) Stuff your wallet with dogeared business cards from establishments like:
a) Take out/delivery pizza joint
c) Liquor store
d) All-you-can-eat buffet
e) Dairy Queen
f) Dunkin' Donuts
g) Taco Bell
j) Drug rehab facility
That way, when the ER staff rifles through your wallet for ID, health insurance, &c., they will instantly see that you are a totally unsuitable candidate to be an organ donor.
iv) Make sure the business cards are broken in to look convincing. Bend them. Get your hands dirty to cover them with smudges.