Mckay needs to be reminded that he doesn't know everything. This is very hard to do, and Radek almost always fails. Radek usually ends up failing even when he succeeds, because no one could call that wounded look that appears in Rodney's eyes every time he makes a mistake succeeding.
Mckay needs to be reminded that he should be nicer to people. This is hard as well, because every reason for it that he gives is met with a contemptuous scowl. When Radek makes the suggestion that he be nicer to people because who knows when he might need something from them, it earns him an aggravated frown from Elizabeth and a moment of consideration from Rodney. Obviously not too extensive a moment though, because it's not long before Rodney's aggravated voice can be heard shattering windows throughout Atlantis's halls ("My God, are you sure you didn't get your degree out of a cereal box, because that would really explain a lot!") and it's Radek's job to have tissues at hand for the unlucky scientist (who really should have known better than to run that simulation at so high a power level).
Mckay needs to be reminded to take better care of himself. This is actually harder than it sounds because, although at first glance it may seem that himself is what he's best at caring for, what he really cares about the most (besides Radek, of course) is science. After a heated discussion about how man cannot live off test results alone, Radek finally just gives in and brings him something from the mess hall, and Rodney's smile is almost like a thank you. It's not just proper nutrition and a full 6-hour sleep schedule ("I don't care what voodoo-man says, I've lived off of 3 hours a night my whole life and I'm not about to change now, or would you rather Atlantis blew up in my sleep?"), it's started to become harder to make sure Rodney doesn't come back through the gate battered and bloody. He's started to take risks, he's started to protect his team, and Radek often has to remind him that he doesn't have to be like Colonel Sheppard. No matter what John says, he's better being Dr. Mckay.
Mckay needs to be reminded that it's ok to make mistakes sometimes. Radek finds this too hard to practice often, and debates on whether or not to keep this one on his list. One day after a particularly disastrous mission, Radek tries to comfort him with a "How else would we learn but through our mistakes?" speech and the raw, angry glare he received shut him up right away. He almost crossed this off his list, but kept it on at the last minute, just on the unlikely chance that one day he'll be able to convince him.
Mckay needs to be reminded that he is loved, and Radek thinks this is the hardest of all. There is no clear way to tell him without sounding sappy, and no subtle way to tell him without him overlooking it. Radek settles for blowjobs and isn't quite sure if that's enough. Radek notices that Rodney's smiles reach his eyes these days and thinks it just might be.