I submitted some tips on this thread:
http://www.canadavisa.com/canada-immigration-discussion-board/please-i-need-a-sample-of-letter-of-purpose-for-visitor-visa-to-canada-t244919.0.html;msg3580441#msg3580441
I, the host, submitted:
-my birth certificate
-my bank statement 3 months
-invitation letter
-employment letter indicating my salary and length of employment
-income tax return from last year showing my salary
-papers showing I own my house
-car registration showing I own a car and can use it to take my wife places
-plans of our upcoming trip to Europe, which further shows my wife not intend to overstay Canada
-proof of booked hotel and plane tickets to Vancouver, which is her first destination in Canada
-15 photos of us together, with family, at wedding
-marriage certificate to show we are married
My wife, the applicant, sent:
-proof of travel insurance
-bank statement, 3 months
-proof of income
-household registry, a document that shows she's lived at her home her entire life (shows family ties)
-household plan, a document that shows her parents have owned and lived at the house her entire life (shows family ties)
-proof of money transfers between myself and her, showing financial support between the both of us
-pictures of her passport showing her entire travel history
-her birth certificate
-her identity card
-MS word letter saying that she did her medical already, please refer to UCI# XXXXXXX for results (this UCI # is the one used for your PR application)
-flight itinerary
-criminal record checks from USA and Vietnam (she lived in US before, these record checks were from our PR application)
Notice a lot of these documents are extra, but we sent them anyway to prove she's not an overstay risk and has no criminal record.