Before packing, make a list of everything you are going to need for your trip. Check out the items as you place them inside your luggage. In packing toiletries, make sure to pack them inside a plastic before you put them it in your luggage. This is to avoid the mess should their bottles burst open during air travel.
Make sure to put in your check-in luggage any essentials that might be confiscated during security checks.
For your Ontario trip, bring very warm clothes if you are going during winter time and light layers for the summer months. Check the internet for the weather conditions in Ontario during the duration of your trip then clothes accordingly.
Bring a backpack with you. This can be a necessity when you plan to go hiking. Also, always arm yourself with a bug spray. There are lots of bugs in the wilderness of Ontario.
Lastly, bring a camera with lots of film. Or if you have the digital kind, make sure you have a huge memory card. There is so much beauty to capture in Ontario.