Hey!
Well, it depends on what you want to do, what you want to visit. Are you visiting family? Where exactly will you go? All those things should be included and detailed in your letter. Also, your letter should explain and emphasize on all your ties to your home country because that is one of the main point CIC will look at. You might also need to explain your financial situation; is anyone funding your trip? If not, you have enough funds to support yourself while in Canada?
All those things should be in your intent letter. Good luck!