#1 ~ Know Your Land:
Always ask for permission if you will be exploring private property.
In Ontario, you are allowed to forage on Crown Land (as long as you do it sustainably - more on this later) but NOT in any Provincial Parks or Conservation Area. The Ontario Foraging Guide is a great place to start.
#2 ~ 100% Plant ID:
Be confident in which plant you are looking at. If you are unsure at all, take a photo, and go home to research. There is a ton of info online and my bookshelf if full of ID books if any of you want to borrow!
This is a lifetime long journey, so start slow and take only what you need.