Each country has specific instructions for the applicant. Most, probably all, require a birth certificate, marriage license, some form of travel documents (passport), plus other country specific docs.
My wife (applicant) sent her birth certificate, our marriage license, her household register (for mainland China applicants), her bio-date page of her passport, our son's notarized birth certificate, a certified copy of our son's proof of Canadian citizenship certificate, and the original receipt for our son's passport application. For me, the sponsor, I had to include *ALL* pages of my passport! I also included copies of our old passports showing visas to Thailand and entry/exit stamps to Hong Kong and Macau. I think that's pretty much it...maybe a few other docs, but I can't remember now.
It can't hurt to send more...what you want to avoid is sending less and then having the VO request those docs later...which would only delay the processing of the visa.
Follow the guides and you shouldn't have any trouble.
FS
I hope that helped haha 