Check out the posts what did you wear and what is the test under the CDN ARMY section, there is a lot of discussion about the process.
But, just to fill you in, I am unsure about the board interview. For the res force, you actually meet with the board and they evaluate your application and ask you questions. I have heard the same is true for the reg force, but I can‘t confirm that. May be one of the otehr guys, such as Ian M or Digger can give you a hand on this one -- they know what is going on.
As for the initial officer interview, the recruitment officer will attempt to judge your character and will ask you questions such as why do you want to join, why do you want to be an officer, explain your leadership skills, how is your work experience relevant to the forces, etc. They will also ask questions about your study/work habits/volunteer experience all the way back through high school -- which is for me a long time ago -- so it is always best to go in with an idea of what and when you did things. The interview is not hard, just be yourself. Some prep is key, however, because you don‘t want to be stumbling along trying to remember when things in your life happened. Try to think of the ways in which your prior experience (i.e. volunteer, work, study, sports, hobbies, etc) are relevant to the forces. It is also a definite plus if you show some lateral thinking skills.