Bills by finanical year
just chucked into a large envelope
honestly I would not bother sorting these too much, there is normally not much reason to go back to them, just keeping them together by year is often enough.

Tax related documents and bank statements by finanical year.
I sort this by individual and by joint info into a lever arch folder with dividers

Mortgage docs, other contracts, pet rego's vacs, initial superannuation details, anything that has reference numbers on it
kept in an accessible folder in case they need to be referred to again

Business paper work, once again by financial year, except for business, gst, rego papers and the like.