Please note these rules only apply if you are NOT the one with cancer. If you have cancer you can act any fucking way you want.
First don't sit and play your iPod Touch while you're waiting for the doctor to come in if you don't know how to turn the fucking thing off. Then when he comes in and laughs (kindly) when you can't figure out how to turn if off (shouldn't the off button take care of this sort of thing?) don't try to merely throw it into your bag at your feet. Because when the only-slightly muffled voices of Wreckless Eric and Amy Rigby continue to waft through the office as talk turns to PSAs you will have to give up and pull it back out and flail at it until the kindly oncologist puts out his hand and says "here" and thankfully turns it off for you. Turns out he's an Amy Rigby fan though so all was still good.
Then when you go to the infusion room and mention to the nurse putting Ernie's IV in that he is supposed to get a Zoladex injection as well, don't get irritated when she groans and says, "oh I know, my lucky day." Then after his infusion when you go into a room for him to get his shot and she continues to complain, over and over, about how much she hates giving these shots and how when she worked nights another nurse always did them for her blah, blah blah...don't get increasingly irritated. Or perhaps try to be clearer than merely dryly saying things like "well, it's not his favorite part of the day either" or "you're really good at inspiring confidence" or even "well, he will probably enjoy it even less than you if that's any consolation." And then when she starts to put a band aid over the spot where she injected the fucking Zoladex, don't say, "you know, I'm sure your job is very difficult but I don't appreciate having to listen to you complain over and over and over about having to give him a shot. You can complain to your colleagues but don't complain to us." And when she sincerely apologizes don't keep going, with your voice rising and tears starting and yell, "I'd be perfectly happy if you never had to give him this fucking shot." And then don't roughly pull the curtain open to wide eyes from the nurses and other chemo patients and stomp through the whole fucking room crying.
Just don't do it.