For example, we learn that G-d made the day (third day following Avraham's Mila) exceptionally hot, so that the ailing Avraham would not be bothered by visitors. Then we are taught that G-d saw that Avraham was disappointed and upset that there were no passers- by, so He sent the angels in the guise of people Avraham's way.

You visit someone who needs bedrest and quiet. You take his phone off the hook so that he won't be disturbed. Nice gesture, but what if that particular person thrives on the social contact of phone calls? You commiserate with the person you are visiting. But what if that upsets her? In short, we must think out a visiting strategy to hope to accomplish the purpose of Bikur Cholim, and not the opposite. Even G-d, so to speak, used trial-and-error with Avraham.

Avraham was hospitable, to say the least. He involved his wife. He involved his child. He said little and did much, rather than the other way around. He treated his guests royally. He escorted them on their departure.

These, and other details are the nuts and bolts of hospitality. We need to work on them, not just the broad concept of Hachnasat Orchim. When to offer. When to push a little. When to ease off. How best to make your guests comfortable. Do mitzvot intelligently.