With the matches you have participated in, did you end up with a final selection of residents by more : a) picking those you really liked b) cutting those you did not like? Does everyone in your program who help choose candidates all say "YES, we like them" or do they talk more about who they really did not like?
It seems to me the candidates are all liked when they are selected to interview, and what stands out most is the dislikes during interview. So it would seem to be the goal to just not blow it and end up disliked. The same way business statistics show a customer that dislikes you will tell roughly twice as many people as the customer that likes you.
The truth is that it is the rare candidate who totally blows it...I mean, who gets drunk at the dinner before, says something offensive or outright tells us he won't be ranking our program. Most everyone else falls somewhere in the middle.
It is certainly easy to "grade" those who totally blow it, and somewhat easy to grade those who just don't interest us. And what interests us (meaning the programs I've been involved in) may differ from faculty member to faculty member but in general there tends to be some agreement about which candidates fit in and those who don't.
The final selection therefore is a combination of cutting those we didn't like (which would have happened at the time of their interview, so they don't even come up for discussion again unless there has been some overwhelming information added since they came for interview) and keeping those we love. It is not one or the other. And candidates are only "liked" in the sense of academics, as I noted in my post above that there is a lot more to being ranked than your academics. I've never met these candidates so I don't necessarily like them but rather can tolerate them because of their file...it takes the interview and their input to make me like them.
Now I can understand where you are coming from that the idea is just "not to blow it". However, I would counter that for most candidates, they must do a little more.
An academic superstar? You'll probably match somewhere unless you are a real social misfit.
An academic loser? You probably won't match unless you have a winning personality, great LORs (which might explain your poor academic record), and a bit of luck.
The vast majority of candidates are swimming around in the middle of the pool and to get into the shallow end where your chances of matching are better, you need to do more than just "not blow it". You need to appear engaged, interested, interesting, the kind of person others like to be around. This means I will remember you more and think of you fondly when I rank you. It won't necessarily mean that you'll end up higher ranked than the guy from the Ivy League with a 245 on Step 1, but it will certainly pull you out of the masses.
So, in the end, I encourage people to strive for more than just "not blowing it" because while yes, I'll remember you if you are seriously inappropriate, I'll also remember those that I just enjoyed interviewing.
I can honestly say that I will never forget one candidate: looked good on paper - PhD, good academic record, well traveled, lot of community activities, etc. but talking to her was like talking to a robot. No engagement, no expression, didn't even laugh at my jokes. I (and other faculty who interviewed her) could just not see working well with her...I'm sure she was bright enough to do the work, but when I'm trapped in the hospital I not only want someone bright and hard-working to be with, but someone that I might actually be able to have a conversation with. Perhaps she was nervous, but I suspect that she was just personality-deficient.