When I swore in, we were asked our relationship status. I put common-law, the Cpl. brought out a form, I brought the form home with me, my girlfriend and I signed it, and when I came to St. Jean I brought a bill with both of our names on it, her birth certificate and drivers licence, our daughters birth certificate, and all my ID. As long as the addresses on your photo ID's match with the address on the bill with both your names on it your good to go. A rental agreement or mortgage with both your names on it is required as well, and if you want to get medical coverage for you spouse bring her medical card or a photo copy of it.
The only problem I ran into was the CFRC only giving me one page of the statutory declaration, that was easy enough to fix though.
In short, when you go to St. Jean, bring everything you can that will assist in proving you two have lived together for over a year and you'll be good to go.