Hi Davidc,
I am filling out the forms right now and I looked on here to see if anyone had any advice for that question as well. Seems like the board is empty when you search for the exact question. (Reasons for attending RMCC)
Have you finished it and submitted it?
What I've done (still in the process) is give a brief story of myself, which leads into why I want to be a part of RMC. I suggest not using any negatives and focus only on positives, just as you would with any cover letter or job interview. Never forget that this is all competitive and you are up against hundreds, if not thousands of people for the same role you want.
I wrote it out one morning, and every time I sit on my computer I open it up again and change something. Take out a sentence, add a sentence, take out a paragraph, add a sentence. I do this with cover letters for jobs I really want as well, or essays for class, because it provides me with the opportunity to look over my work in many different moods and states of mind. Because what can seem like a good idea or sentence structure or word choice may not always seem like such a great idea even an hour later. I've taken time to perfect this part of my application as I feel it is the most important part. Maybe I'm off base, but I think that hundreds of people will have similar sports, music and leadership histories as I do (if not better!) even though I have an impressive list. If we are all similar, the only difference will be the reasons why we want to attend. And you know that there will not be many differences in why some people want to join. So, while striking a balance of reiterating your achievements/outstanding abilities with positive personal feelings about why you want to be part of the Canadian Military system you can separate yourself from the rest of the applicants that don't give it as much thought.
I'm 25 and I've got some maturity on most of the applicants in not only age but work experience, and hopefully this is something that some younger kids read and utilize on their application. Be honest and thorough. My application will go in 3 days before the deadline, despite the fact I was done and ready weeks ago (Pilot ROTP, Nov 18, 2012 deadline).
Good luck to all.
Alex