I try at least to arm myself with enough knowledge about their case, their problems, what the treatments plans are, etc, so that I can discuss with them the plans. If I go in "blind," I ask them for time to review their case, explain to them that I just came on, dont' know their case, etc. MOST people will understand and give me time to get caught up. Then I can investigate, find out what's wrong, try to help, etc. With most reasonable people, it works.
I also don't get too friendly lately, EVER. I am professional, friendly, but not a "friend" to families. I am their nurse, try to be their advocate, but I'm not their friend. I have been burned from being too friendly with those who simply turned on me in a flash when things started not to go well.
With some who get unreasonable, I will try to politely reason, try to politely provide explanations, and often I can turn them around and get them to calm down. I will try to listen to them as much as possible, see their point of view, etc.
The ones that TOTALLY get me are the ones who complain about the food. I mean -- it's SO childish to me to complain about a hot meal -- who CARES if it's not restaurant quality -- most of it is edible, at least -- and if they are well enough to complain about it, IMO, they aren't even sick enough to be in the hospital in the first place. Just my opinon -- just grinds my gears to no end.