#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.
#3 ~ Express Gratitude:

Foraging reminds us that mother nature gives freely and abundantly. Before harvesting, take a moment to show appreciation for the plant.
This can look different for everyone. Some people say a prayer, sing, or leave tobacco. I like to thank the plant, and leave a piece of my hair. Little by little, the connection between you and the plant will grow stronger.