Couldn't agree more with sore eyes...pretty much nailed it by talking about being real likeable rather than fake likeable. It's challenging to think about 6-12 back-to-back interviews on any given interview day. I've come to realize that there are some interviewers that are really good at interviewing and some that don't have a clue how to interview...you have to be able to connect with both.
You'll get the group (good interviewers in my opinion) that will just be good at starting and holding a conversation and so you have to be comfortable with yourself, first and foremost. The conversation is free flowing and doesn't not seem pre-contrived...in effect they allow you to ease up and bring out your real personality a little more. Then you'll get the group that need a security blanket of a canned set of questions that they have pre-made (bad interviewers in my opinion). I think these interviews are pretty useless because they are so generalized and individual personalization is lost, especially if you compare to the good style of interviewing. The problem with this style, and it's used at some of the big institutions, is that the interviewer is on edge and you get a sense of their "game face" but not as much about who they really are. I think good interviewers make it conversational and still learns what they would like to know about you. That being said, you have to be good at dealing with both styles of interviews. Be humble and confident in yourself and if you can project that, you will be "real likeable" in either scenario.
That sounds really philosophical

and so here are some practical points outside of content and more on the art of interviewing (these are just my opinions and nothing more):
1. Don't try too hard. If there is some silence while the interviewer is looking at something in your applications, don't fill up the silence with constant talking. It shows confidence to be comfortable with silence and it gives the interviewer a chance to process his question. Again, a good interviewer rarely puts you in such a spot but you're up against both good and bad interviewers. Don't cut the interviewer off mid-sentence...you'd be surprised how often this can happen. You'll get co-interviewers that will constantly cut others off mid-sentence and that's also a clue. If the interviewers get the sense that you only like to hear yourself talk, it's a good guess that the ranking meeting will not go well for you.
2. Body language is huge. If you sit in a closed off fashion that does not come across very confident. Simply mimicking the interviewer or having them mimic you is a big plus (sit up when the other sits up, lean forward when the other leans forward, etc.). Again it shows that you are in tune with the other person and this comes across as confidence.
3. Have a strong voice when it is your turn to talk. When you are asked to discuss your research or a project or just to elaborate more on some work that they find interesting, then talk about with a strong voice. Some people only talk in questions for every sentence, even if they are not asking a question...all of us have met someone like this and so you know what I mean. If you do this, practice with a friend that will be critical of you. Have them ask you questions and see if you respond with a confident voice and work on it.
4. You may get interviewers that will criticize you during the interview. It may be a test or might not be. I wouldn't waste my time to figure that out. Remain calm and do your best to take their criticism and keep a positive tone to your voice. If you become negative, it will bring the interview down. Also, if you really feel negative energy from an interviewer, you may want to reconsider that program if that person is a important part of resident education. I know that we can't be choosers in dermatology but you can be more of a chooser than you think.
Sometimes the intangibles are more important than the content and that's why I think that good interviewers focus on more than pre-set questions so that they can really see the whole package....regardless, good luck with your interviews and I look forward to meeting some of you on the interview trail.