"There are no articles on finding the right thing to say. However, there are plenty of articles on what not to say. Theres one that even has a diagram of concentric circles to show which way the talk should flow. The affected person is at the bulls-eye; arrows indicate comfort should flow inward, while anything involving complaints, unhappiness, or other less-than-comforting talk should go the other way. Youre supposed to figure out which circle youre in with respect to the people around you, and talk accordingly.
As the person located at the bulls-eye, if I may be so bold: this is a great exercise in shutting people up."
Personally, I find that this stuff comes in waves. In the first few weeks of diagnosis, I really couldn't cope with anything except quiet, even silent, support. Then it got better, and I was able to engage more with people, some of whom had complicated, emotional reactions. I expect when chemo starts, I may need to pull back again. And back and forth, on the waves of treatment / illness.
If you're someone who says the wrong thing at the wrong time, it may be less than helpful. But staying silent for fear of saying the wrong thing is a bit sad too, and I imagine could leave sick people feeling isolated.
Just feel your way through, reading the cues as best you can. Don't cut yourself off, or cut them off. You're not likely to say / do anything too terrible.