I don't know how anyone makes it out of a hospital alive without someone to advocate for them. It's especially important if the patient is elderly, a woman, or a minority. Basically anyone that isn't a white, straight man under 60, because if you aren't in that small group you're far more likely to receive substandard care.
One of those pamphlets or papers they give out in admittance will contain the number for the hospital ombudsmen or patient advocate. Save that! I had to contact them when they twice messed up a test prep for my grandfather by giving him food when he wasn't supposed to have any so they couldn't do the test. He was moved off that floor to the cardiac wing of the hospital, even though he wasn't in for cardiac care that time, in less than an hour after I called the ombudsmen. It was a much nicer room, and the patient to nurse ratio was better too. Document everything, and be firm but calm.
Don't be afraid to ask for a second opinion or another doctor. The best resource I found was to ask all the nurses which doctor they would use for their grandfather etc. I found him a different heart doctor doing that who was so much better than do nothing doctor he had before.
I've found, "How would you want your grandparent, sister, daughter etc treated," to be a bit magic in terms of getting them good care in general. I've literally seen medical people pause, and rethink what they're going to say after I phrase it that way. Also, women doctors generally spend more time listening to patients. I'm not saying that's always true of course, but there have been studies backing that up, and it's certainly been my experience as well. I went with my grandfather to an appointment with his GP, and reported all these symptoms I was seeing. He literally laughed in my face, and circled his age on the chart. I took him to my doctor, a woman, and it turned out he had Parkinson's.
The Internet is your friend, provided it's a legitimate medical site like the Mayo or Cleveland clinic etc. I saved my mother's eyesight finding an off label usage for a med, and found some stuff my vet ended up using for other patients.
Sorry if I this too long winded! I've unfortunately have a lot of experience caretaking.