If you are companioning a loved one as they leave this world I hope this can act as a sort of road map. Death is highly individual but has some similarities. Not everyone will exhibit all these symptoms but everyone wil have some of them, unless it is a sudden death.
I like to think of things in terms of the elements. The Buddhists believe that a very intricate series of processes happen as the soul unties itself from the bonds of the body. If you are interested in this subject I recommend reading Dying with Confidence by Anyen Rinpoche.
The first element to leave the body is earth. Your ability to walk, stand and even get out of bed and contact the earth leaves you. Your body loses the ability to support itself. This is a slow process and happens over the course of weeks. It is during this time that people become slowly disinterested in eating food. Ultimately the food just rolls around in the mouth with not enough saliva to process it. I will never forget my husband Rob looking at me with a mouth full of food and a sad look on his face. He said, "Its disgusting." We switched to smoothies or fresh fruit that had a lot of liquid of its own. As a hospice volunteer I see a lot of anxiety around food, and a lot of dying people trying to eat to soothe their worried caregivers. Please, please let the person decide for themselves what feels right. Forcing them to eat is not going to prolong their lives, but it may make some of that precious time "disgusting". Sometimes as people lose the ability to be ambulatory they go thru a very restless stage. They can't get comfortable. There is a lot of moving from chair to bed, or writhing around on the bed. This is part of the process of dying. Rob described it as "the most miserable flu ever". I did a lot of back rubs, foot rubs and palm rubs, but its a stage and they have to go thru it.
The second element to leave is water. The mouth dries, and eventually they lose the ability to swallow, tears dry up, Its important at this time to keep the lips moist with vaseline and hospice will give you biotene mouth swabs. Biotene is a lubricant that also freshens the mouth. Ice chips are also helpful. Towards the very end they have their last output of urine and it is frequently very dark.
The third element to leave is fire. Frequently people spike a fever or chills at the end as their body loses the ability to regulate temperature. Hands and feet can get cold as blood starts to be shunted to the organs. A cool washcloth on the forehead or an extra blanket can be all they need.
The final element to leave is the breath. Breathing goes thru many changes as death nears. It can be labored, shallow and rapid and everything in between. As a companion it can be alarming, especially the "death rattle". This is caused by secretions being trapped because they can't be cleared by swallowing anymore. You can turn people on their sides, ideally the left side to help clear this. But be comforted by knowing that it does not bother them. There are also medications to dry the secretions up. The Zen hospice center will sometimes do a meditation where they place their hand lightly on the persons chest and lean close and audibly exhale with every exhale of the person as a way to slowly calm their breathing if it seems anxiety driven. Or place their hand over the persons chest and say "I am here. You are here. We are here." Obviously this is something you would have to ascertain whether the person would be soothed by this ahead of time. One thing about the breath that first timers might be surprised by is that the inhaled breath can stop and there can be quite a lag before the final exhale. Sometimes up to what feels like a minute and then a loud sigh/exhale. It can come as quite a surprise.
The Buddhists believe that for some people the soul leaves through the crown of the head. For this reason they give a light tug to the hair on the top of the head to encourage the soul to move in this direction. Sometimes death shows up in the face. The face can take on a bluish hue or the cheeks can be red from ruptured blood vessels. Others have death show up in the feet and hands. They swell and become cold and then mottled purple and dark blueish. The signs of death are many and varied. Even with signs it is highly unpredicatable. People can hang on for days and weeks perhaps because they feel they have unfinished business. For this reason it is important to have those conversations while they are still lucid and able to talk. Ask them "Is there anything you are afraid of?" "Anything you are worried about?" "Anything you want to do with the time you have left?" Don't worry that you will be 'giving up' on them. In general dying people know they are dying and want to be seen as such.
Remember afterward there will be regrets about things you did or didn't do. Try and forgive yourself, your loved one would not want you to waste one moment in regret. Most likely they were deeply thankful for having you by their side. This is one of the reasons I recommend people facing the end of their lives to write a letter to their health care proxy absolving them of any and all regret/guilt. There are many right ways and everybody is just doing their best. Amen.