Hi there,
Here is my two cents -
1. Interview:
a) Your attire (in my opinion) should be business formals. Clean, pressed and well matched. Black shoes go with a black belt, tie should compliment the trouser and shirt, etc. While this an interview for a job in the military and not the fashion industry, most hiring managers in any industry prefer a well turned out candidate.
b) Be prepared. Know the job, the organization, the working environment, the regiment or squadron that you're aspiring to join and most of all - know yourself. When I was in the RC waiting to be called in for my interview I was chatting with another person who was also there for an interview. He was dressed in torn jeans and I was surprised that he there for an interview and not just information gathering. I happened to ask the guy why he wanted to be an "infanteer", and the person said "Ummmm.... I don't know". That person did not get selected. I cannot give specifics about the content of the interview, but I will say this - if you've done your homework with sincerity, you will excel. There is tons of information on the Internet specific to the CF interview. I do not wish to post the specific link here, because I think that it will be a breach of privacy. If you speak with the interview booking NCO, he/ she will point you in the right direction.
When I went for my interview, I took along a file of documents (reference letters, commendation letters from supervisors and managers, additional courses undertaken through work, yearly appraisal report, etc). For most of the questions that I was asked, I had a document to support my answer and the actual work example that I had cited. I can say one thing for a fact - MCCs like candidates who come in well prepared.
2. Fitness:
a) I can't say if your physical fitness test will be on the same day as the interview. For my wife, she was scheduled for the CFAT and medical on the same day. Speak with the booking staff. They will tell you what all is going to be done and for how long you will need to be in the RC that day.
b) As for push ups, don't worry too much but just keep working on it. Weight training really helped me. You should aim to be able to cleanly bench press at-least your own weight (eight reps minimum). By cleanly, I mean - get the bar off the rack your self, do slow and controlled reps touching the bar to your chest everytime, and finally place the bar back on your own. Several of my friends who're in the CF have told me that 60-70 push ups is the number that most instructors look for in Recruits/ OCdts during basic training. Another thing to incorporate in your training is chin ups. You will not be required to do any push ups during testing. However, during basic training based on age and gender there is a minimum that one is expected to be able to do.
Just a little about myself - I have been in the recruiting process for almost three years now. (I am a DEO Regular Force candidate). During this time, I have been through three interview boards, merit listed all three times and have even been selected by a national board. Some work still needs to be done on my file that is why I have not been enrolled as yet.
Again, all this is only based on my experience. I am not in the CF and am certainly not a recruiter!
Take care and all the best to you.
AGB.