I have thought a lot about this mainly because I had many people that I consider to be my caregivers. I have had the good fortune to be able to talk to them at length about what it was like to be on the other side of my illness. What they told me was to some extent quite shocking because I never saw most of it.
So for my advice to any caregiver not just someone dealing cancer but any major illness would include a number of things.
1.) I know that most people believe that only showing their strong side and being the "strong" one who will be the best. However I can't tell you how reassuring it was when I could share a cry with my family. Yes there is a time to be strong but it is also nice to see that this is affecting them as much as it is affecting me.
2.) Think about how you would want to be treated if it were you in the situation. I think this helps with not only your perception but also how you talk and act towards whomever you are caring for. I know from a cancer point of view there were some severe side effects that often I couldn't control and some of them affected my mood, actions, etc. So it helped when my family and friends were understanding about things like that.
3.) Offer support in the way that you are comfortable with. I had a variety of caregivers that each one was better at something than the other. A really good friend of mine happens to be someone who doesn't know a whole lot about the medical world so she was more helpful by just keeping me company, sharing stories, and even helping by bringing meals.
4.) One thing that really helped me was when people wouldn't treat me as though I was sick. There were sometimes when that wasn't an option but for the most part it was nice to be treated "normal". It gave me that small little moment to forget what was going on and often just have fun.
5.) The last thing I would recommend would be that as much as it is important to take care of the patient you must also take care of yourself. Most often dealing with any illness it is an emotional rollercoaster for the caregivers as well as the patients. There are many resources out there that offer help in these areas for caregivers. But this can also mean taking some time for yourself. Often I think as people we get so wrapped up in putting others before ourselves that sometimes it can back fire on us. Take a little you time, go to a movie, out to dinner with friends, get a manicure or massage. Have a little time to forget what you are currently going through and have a little fun.
I have to also mention that I consider my medical team as part of my caregivers as well. I am not really sure if there is anyway to give them advice because they are most often trying to be as professional and reassuring as they can. The only thing that I can say to them is that as a patient it is a very personal experience. It helped me to be able to get to know my doctors and such on a more personal level. So don't be too caught up in sticking to straight and narrow share a little about yourself with your patients.
Anyway those are just my thoughts hope they were helpful to some.