... I'd suggest to read the Guides: (
http://www.cic.gc.ca/english/information/applications/guides/3999E3.asp)
Some documents and forms are specific for the country/region you're applying from. For example one of the Region guides states: "If you are being sponsored by your spouse, common-law partner or conjugal partner, you must send evidence of the relationship between you and your sponsor such as wedding photos or proof that you are partners, letters between you and your sponsor, and telephone bills showing contact between you and your sponsor."
Make sure to select the appropriate guide for your region, example United States, South East Asia, East Europe, etc.: (
http://www.cic.gc.ca/english/information/applications/fc.asp#region) ......