I don't have definite plans and do not have friends/family that I'm planning on visiting in Canada.
With Canada, like most Western countries the issue is not 'here is what you must do to get a visa', it's about convincing Citizenship and Immigration that you are a genuine temporary visitor, that you intend to leave when your visit is over and that you will not work or do anything else illegal. The more evidence that you can provide about your intentions the better chance you have of getting a visa.
If the only thing you tell CIC is "I have no idea how long I'm going to stay or what I'm going to do", then your chances of getting the visa are much reduced. If you can say "I intend to depart on this day (within limits of a tourist visa) - this is what I'm intending to do and here is evidence that I really am going to do it" your chances of getting a visa are increased.
In particular almost all genuine visitors know when they intend to leave, and will have a return or onward ticket booked. Not doing that reduces your credibility. LIkewise most genuine visitors have some idea of what they want to do (otherwise why would they come to Canada rather than another place).
You are free to submit as much or as little evidence as you feel like, but the more you submit the greater your chances of getting a visa.