Forage in State Parks:
While it's been legal to forage off-trail for a while, the old rules were a bit confusing for amateur foragers. Now, all the rules about foraging off-trail are done away with, so you can feel free to go where the good eats lead you. That said, DNR officials warn against amateur hikers going too far off the trail, as this could get you lost and end up with a way bigger problem than not finding any morels. If it's your first time in a big park, go with an experienced forager or hiker who will be able to lead you back to a trail.
Forage at the edges of woods
Right along the edge of any wooded area, there is usually a nice mix of forageable foods. The spot where Matt showed me what to look for was at the wooded edge of a public park, and that mix of direct sunlight and a little shade makes for an ideal mix of full- and partial-sun plants.
Forage in unfertilized or treated "green space"
Since you can forage anything from violets in open fields to pine needles, the world becomes your grocery store. You'll want to stay away (obviously) from private property, but as long as the land hasn't been sprayed for anything, you should be alright.
Forage too close to a major road
This is pretty obvious, but there are a lot of icky things in the soil and air around major roadways, so avoid foraging along major thoroughfares. It's just as much a personal safety issues as a food safety issue. Plus, no one likes a salad that tastes vaguely of motor oil.
Don't eat out of "manicured" green space
It sounds appealing to go out and forage in your cul-de-sac, but wherever there is uniformly green, perfect grass, there has probably also been some sprayed treatment. Lawn chemicals are also made to stick to the grass even when there's rain, so don't think you're going to rinse all that stuff off. When it comes to suburban foraging, it might be worth the drive or bike to get away from artificial lawn care products.
Forage a spot to death
This goes without saying, but unless you're foraging for specifically invasive species, you should spread out your foraging beyond just one small space. After all, the point is to become more connected to the earth around you.