If you are going to stay with relatives, include a letter from them saying you can stay with them. If you are planning on renting/buying your own place; include searches of rental properties/houses in the area you intend to live in that are in your price range. Write a letter explaining why you included these as examples.
I am going back to school to do a master's program so I included correspondence from the university. We also included quotes from moving companies about moving our stuff over. We also have a pet and included quotes from companies and a letter of explanation on how to get him over to Canada.
If you have a job offer, include that. If not, we included examples of jobs available in our area(s) of expertise. Showing that we had researched/planned our lives ahead of time. In our letter, we also wrote about our plans in 3 stages. What we will do initially when we move over (live with a relative, apply for the jobs used as examples and visit organizations that help new immigrants (some places help get health cards or help integrate into the community- you can include information about these groups and what they do in your application as further proof ). Next stage was where we planned to be in a month after that (hopefully in jobs and looking to rent/buy) and then in the future (we said that we wanted to have kids in Canada since I am closer to my family ext).
Hope this helps!