a male human wrote:I don't quite know how much energy to display in an interview. Energetic and smiling hard? Calm and relaxed (and smiling)?
Please don't take this the wrong way, but have you done a lot of practice interviews, preferably with alumni? Several of your posts indicate that you've lost your way a bit on norms for interviewing -- completely understandable, but it should be a priority for correcting. You need to be able to trust your instincts (or at least know where/when they lead you astray so you can instantly course correct). Alumni who offer to be contacted are generally very welling to help out and if you let them know that think your interviewing is not reflective of your abilities and you are looking for some constructive criticism, you should be able to find some people to help you out. (I would skip your career services office -- they are usually very disconnected from what people who actually do interviews think).
Anyway, the easiest way to usually strike the right balance is to employ mirroring.
Since there is a "position" differential between an interviewer and interviewee, I think the following is a good rule of thumb: for enthusiasm, be just a little bit more enthusiastic than your interviewer. They work there. They aren't going to gush. You want to sell your desire to work them, but not oversell. If you have a very effusive interviewer, try to match their level. If you have a very reserved interviewer, dial it back so that you aren't overwhelming them. Exceptions: if someone is so far outside your normal range of showing emotion, don't mirror if it is going to make you seem fake -- just dial back (or amplify) your own tone to whichever end of your spectrum is appropriate.
Level of formality is similar. You want to be slightly more formal than the person interviewing you. By mirroring their level of formality/informality and then being slightly more formal, you should strike the right balance of showing respect without seeming too uptight. Exception here is if you have someone totally informal/inappropriate. Do not let your guard completely down and swear or badmouth or otherwise head down an unprofessional path. Stay on the more relaxed end of the spectrum, but don't mirror that type of behavior.