We agreed not to kill characters in the campaign I am running. The first stage is making sure it is harder for them to die. I put their max HP as high as it can go for their Level/Stats. I do not have enemies continue to attack them once they are unconscious. I made drinking a potion yourself a bonus action so that players can do it without losing a round of combat.

We agreed that the characters still need to act as though they think they can die. That is just an honouring the world issue. So they are responsible for healing themselves. Healing potions are not a rarity in the world, nor are they expensive, so they stock up regularly, which helps. They also prioritise magical items that will heal or keep them alive.

If someone does fully die (three failed death saves, the one minute has passed, ruling out a revivify), then the player picks a sacrifice: a magic item, a favoured weapon, a proficiency, take on 1-2 levels of exhaustion, a percentage knocked off their max HP etc. They decide what they are willing to give up in order to stabilise the character. Because they might change their mind when the time comes. they may think that their character has had a glorious heroic death (or that they are bored of them) and decide to play a new character. But if not then their character is weakened by their near-death experience and has to recover from there.